The Israeli army carried out an airstrike early Tuesday, killing a commander in the Al-Quds Brigades, the armed wing of Gaza-based resistance faction Islamic Jihad.
The military said it struck a house in Gaza City to target Bahaa Abu Al-Atta, in a resumption of targeted killing.
The army said the attack "was approved by the Prime Minister and Defense Minister Benjamin Netanyahu."
"Abu Al-Atta practically carried out most of the (Islamic Jihad) movement's activities in the Gaza Strip..., and he was directly involved in the operations and attempts to target the citizens of Israel and IDF (army) soldiers in various ways," a military statement said.
The Palestinian resistance group confirmed that Al-Atta, its north Gaza Strip commander, was killed and vowed to avenge his death.
"We mourn Commander Abu Al-Atta and his wife who were martyred in this crime, and we announce the state of alert among our fighters," it said in a statement.
A father of five, Abu Al-Atta was born in Shejaiya neighborhood in the eastern Gaza Strip in 1977.
In 1990, he joined the Islamic Jihad and moved up until he became its commander in the northern Gaza Strip.
Abu Al-Atta had previously survived three Israeli assassination attempts, the last of which was in 2014.
In another statement, Islamic Jihad's military wing Al-Quds Brigades said it fired rockets into southern Israel in response to the assassination.
Red alert sirens were activated in southern Israel following the airstrike, the Israeli army said.
A state of emergency was declared in the Gaza Strip and schools were suspended until further notice.
The official Israeli Broadcasting Corporation said the army had reinforced its forces around the Gaza Strip and was preparing for several "offensive and defensive scenarios."
Meanwhile, a Palestinian government spokesman said President Mahmoud Abbas was holding contacts to halt the Israeli military escalation in the Gaza Strip.
"We call for urgent international intervention to stop the Israeli crimes and escalation that could lead to a new war that kills our people in Gaza," Ibrahim Melhem told Anadolu Agency.
Palestinian group Hamas, which rules the Gaza Strip, described the Israeli attack that killed the Islamic Jihad commander as a "serious escalation".
"The Israeli occupation bears the responsibility for this crime and its repercussions," Hamas spokesman Sami Abu Zuhri said on Twitter.
Saeb Erekat, Secretary General of the Palestine Liberation Organization (PLO)'s Executive Committee, also condemned the Israeli airstrike.
"We condemn in strongest possible terms the cowardly assassination of the Islamic Jihad commander and his wife," Erekat said in a statement.
The Organization of Islamic Cooperation (OIC), for its part, described the Israeli attacks as "a blatant breach to international humanitarian law and international treaties".
In a statement, the OIC held Israel "totally responsible for the consequences of this serious escalation" and called on the international community "to shoulder responsibilities to provide international protection to the Palestinian people".Anadolu Agency website contains only a portion of the news stories offered to subscribers in the AA News Broadcasting System (HAS), and in summarized form. Please contact us for subscription options.