ANKARA

Indian police are investigating Monday's blast in the capital, New Delhi, that killed at least 12 people and injured many others under anti-terrorism law, state media reported.

“A first information report (FIR) has been registered under the UAPA (Unlawful Activities (Prevention) Act), Explosives Act, and Bharatiya Nyaya Sanhita (BNS). Investigation has been taken up,” state-run Doordarshan News reported, quoting Raja Banthia, a top Delhi police official.

He said the investigation is at a "very preliminary stage and any comment on that would be too premature.”

The blast took place outside the Red Fort, a historic Mughal-era structure, on Monday at around 6.52 pm (0122GMT), according to the police.

A popular tourist destination, the Red Fort has been closed for three days until Nov. 13.

According to the Press Trust of India, the death toll climbed to 12 on Tuesday.

Prime Minister Narendra Modi assessed the situation during a phone call with Amit Shah, the home minister.

"Our agencies will get to the bottom of this conspiracy. The conspirators behind this will not be spared. All those responsible will be brought to justice," said Modi, addressing an event in neighboring Bhutan. He is on a two-day trip to the landlocked nation.

Security has been tightened nationwide following the blast, and key establishments and several regions remain on high alert.

India’s Central Industrial Security Force said installations secured by the force, including Delhi Metro, Red Fort, government buildings, and Delhi airport, have been placed on high alert.

Delhi Police Commissioner Satish Golcha said a slow-moving vehicle had stopped at a red light, which triggered the blast, leading to fire in several vehicles.