Leaders from around the world have issued statements condemning Saturday's terror attacks near a football stadium in Istanbul that martyred at least 38 people and injured 155 others.
In Washington, the White House condemned the attacks "in the strongest terms", and pledged solidarity with Turkey.
"Our thoughts and prayers go out to the victims, their families and loved ones, and to all the people of Turkey," National Security Council spokesman Ned Price said in a statement.
"We stand together with Turkey, our NATO Ally, against all terrorists who threaten Turkey, the United States, and global peace and stability."
In a separate statement, U.S. Defense chief Ash Carter said that Saturday's attacks "only redoubles our resolve to stand shoulder to shoulder with our Turkish allies in condemning these attacks and relentlessly combatting terrorism."
On his Twitter account, Canadian Foreign Minister Stephane Dion said Canada strongly condemned the deadly attack in Istanbul.
"Our thoughts are with victims and families and the people of Turkey," Dion said.
'Thoughts and solidarity with Turkish citizens'
The president of the European Parliament posted a comment on social media. "My thoughts & solidarity with Turkish citizens, with families of victims of Istanbul attacks. I wish speedy and full recovery to the injured,” Martin Schulz said.
A spokesman for Council of Europe secretary general said Ankara would find support from Europe. "Turkey can rely on the solidarity and support of European governments and the Council of Europe after today's Istanbul terrorist attack," Daniel Holtgen said.
"All our solidarity to all citizens of Turkey," EU High Representative for Foreign Affairs Federica Mogherini posted on her Twitter account.
NATO Secretary General Jens Stoltenberg condemned the attack, calling it "horrific acts of terror." He stressed that NATO stood united in solidarity with its ally Turkey. "We remain determined to fight terrorism in all its forms," he added.
U.K. Foreign Secretary Boris Johnson said the "U.K. [was] committed to working with Turkey to tackle terrorism," adding that his thoughts were with all those affected.
In a statement, UN Secretary General Ban Ki-moon expressed his deepest sympathy and condolences to the families of the victims. "He hopes that the perpetrators of this terrorist act will be swiftly identified and brought to justice," the UN website reads.
France, Germany, Russia, Pakistan condemn attack
On his Twitter account, French President Francois Hollande denounced the blasts, showing his support to Turkey.
German Foreign Minister Frank-Walter Steinmeier condemned the attack and said Germany was mourning with Turkey.
German Chancellor Angela Merkel expressed her condolences to President Erdogan during a phone call Sunday.
Russian President Vladimir Putin also expressed condolences for those who lost their lives, condemning "this cowardly, cynical crime".
Azerbaijani President Ilham Aliyev decried the attack and urged for "a resolute fight against any kind of terrorism".
Kazakhstan President Nursultan Nazarbayev and Georgian Prime Minister Giorgi Kvirikashvili expressed condolences to the families of the victims and added they were ready to show support in Turkey's fight against the terrorism.
The Malaysian government also strongly condemned the attack, calling it "inhumane" in a statement issued by the country's Foreign Ministry.
“The Malaysian government expresses its deepest condolences to the government and people of Turkey, as well as to the families and victims affected by the attacks," it added.
Pakistani President Mamnoon Hussain also condemned the blasts saying the terrorist attacks cannot shake the resolve of Turkish people and the government in their war against terrorism.
In a message issued on Sunday, Pakistani Prime Minister Nawaz Sharif expressed deep sorrow strongly condemning the attack.
Noting that the Pakistani people were extremely sad, Sharif said that Pakistan was in solidarity with the Turkish people and government.
In a statement, Pakistan's Foreign Ministry also condemned Saturday's terror attack, stating that Pakistan "is in solidarity with fellow Turkish people."
Highlighting that "those who want to undermine the unity of Turkey will never succeed," the statement said Turkey "will defeat terrorism with its unshakable will."
Pakistan's Embassy in Turkey also issued a statement condemning the terror attack in Istanbul.
"Pakistan condemns this heinous act of terrorism in the strongest possible terms. Our thoughts and prayers are with all those who have lost their loved ones. We extend our profound sympathies and condolences to the brotherly people and Government of Turkey. We also pray for the speedy recovery of those injured," the statement said.
In a statement issued on Sunday, the Singapore Foreign Ministry strongly condemned the attack in Istanbul and expressed condolences.
UEFA condemns 'horrible act'
On Twitter, European football's governing body, UEFA, "strongly" condemned "the horrible act" and sent its support to the Turkish Football Federation, Besiktas and Bursaspor football clubs.
"UEFA would like to express its deepest condolences to the families of all the victims of tonight's bombing in Istanbul," it said.
Lithuania, Ukraine, Spain, India and Sweden condemn attack
Lithuanian President Dalia Grybauskaite expressed her condolences in a message she sent to President Recep Tayyip Erdogan.
On his Twitter account, Ukrainian President Petro Poroshenko strongly condemned the terror attack in Istanbul, saying, "there cannot be a justification" for it.
The Spanish Prime Minister Mariano Rajov condemned the attack and said on his Twitter account that "Solidarity against barbarism and terror. We would like to send our sincere solidarity and support messages to Turkish authorities in these difficult times."
Indian Foreign Ministry also condemned the terror attack in Istanbul in a statement.
"Terrorism is wholly unacceptable, whatever the type and declaration. The shameful attack in Istanbul underscores the need for the world community to find a common solution to the scourge of terrorism."
The Swedish Foreign Minister Margot Wallstrom condemned the attack in her Twitter account and expressed her condolences for the victims.
Portuguese President Marcelo Rebelo de Sousa on Sunday also conveyed a condolence message to President Erdogan.
OIC, Turkish Republic of Northern Cyprus condemnations
The Organization of Islamic Cooperation (OIC) condemned the bomb attacks in Istanbul "in the strongest terms."
Expressing his sorrow over "these criminal and cowardly acts that run contrary to the spirit and teachings of Islam and humanity," the Secretary General of the OIC, Yousef A. Al-Othaimeen offered "his sincere condolences to the families of the victims, the Government and the people of Turkey" and wished early recovery to the injured people.
Al-Othaimeen further reiterated the principled position of the OIC against all forms and manifestations of terrorism.
A day of national mourning has been declared on Sunday in the Turkish Republic of Northern Cyprus (TRNC). The national flags will be flown at half-mast across the country on Sunday.
Middle East reactions
Lebanon's Future political movement, known also as Al-Mustaqbal and led by former Prime Minister Saad Hariri, condemned the attack in a statement on Sunday.
"Terror is killing people without discriminating between Muslims and Christians and trying to destroy communities by dividing them," Hariri said.
Hariri urged the international community not only to combat terrorism but also to fight crises and wars at the same time, stressing that "they are in solidarity with the Turkish government in the fight against terrorism."
In a statement, Egyptian Foreign Ministry Spokesman Ahmed Abu Zeyd expressed solidarity with Turkish people and called on the international community to prevent the terror organizations.
"Egypt strongly condemns the attacks in Istanbul and reiterates its stance against terrorism that threatens international peace and security."
Qatar Emir Sheikh Tamim bin Hamad Al Thani, Palestinian President Mahmoud Abbas and Hamas Political Bureau Chief Khaled Mashal expressed their condolences to Erdogan during a phone call Sunday.
Saudi Arabia also condemned the attack describing it as "unacceptable".
According to a statement published by Saudi state-run SPA news Agency, Saudi Arabia said it stood by fellow countries against terror attacks.
Kuwait, Afghanistan, Iraq, Israel, Iran, Jordan, Bahrain, the United Arab Emirates (UAE) and Tunisia also condemned the attack, showing solidarity with Turkey.
Hungarian Foreign Ministry spokesman Tamas Menczer said the attack was committed against the European Union as well. "The security of Europe starts with Turkey's stability," he said.
Kosova President Hashim Thaci expressed his concerns over terror attack in Istanbul.
"Kosova stands by Turkey in times of joy and in these disturbing moments. Justice shall prevail," he said in his Twitter account.
In a letter of condolence to Erdogan, the chairman of the Bosnia-Herzegovina Presidency, Mladen Ivanic expressed his sorrow over the attack that claimed the lives of many people.
"Terrorism and extremism are threats to global security without borders, so it is essential to fight jointly against this threat," Ivanic said.
Describing Turkey as "friend and ally", Romanian Defense Minister Mihnea Motoc "strongly condemned" the terror attack in Istanbul, "which had no excuse and could not reach its aims."
In his Facebook account, Motoc said Romania "stands by Turkey in its fight against terrorism."
The Greek Foreign Ministry said in a statement that Greece "stands with all its friends and neighbors during their difficult time."
Greek Prime Minister Alexis Tsipras expressed his condolences over the terror attack in Istanbul to Turkish Prime Minister Binali Yildirim during a phone call.
At around 10.30 p.m. (1930GMT) on Saturday evening, two explosions rocked Istanbul's European side.
Outside a football stadium in Istanbul's Besiktas district, a car bomb was detonated two hours after the end of a Turkish football league match between Besiktas and Bursaspor.
Seconds later, a suicide bomb attack occurred in Macka Park in the same neighborhood. The suicide bomber blew himself up after police noticed him, according to Interior Minister Suleyman Soylu.
"A total of 13 suspects have been arrested so far," he said. "Signs point to the involvement of the PKK terrorist group."
Deputy Prime Minister Numan Kurtulmus also said Sunday that the PKK terror group was "most likely" to have been involved in Saturday's deadly terror attack.
The Turkish Prime Ministry said in a statement, a day of national mourning has been declared on Sunday. The national flags will be flown at half-mast across Turkey and at foreign delegations, it added.