NEW DELHI - Indian Prime Minister Narendra Modi on Tuesday called a deadly car explosion in the heart of the capital that killed at least eight people a "conspiracy", vowing those responsible will face justice.
Police are yet to give exact details of what caused Monday's blast near the historic Red Fort, one of India's most well-known landmarks, and the site of the annual prime minister's Independence Day speech.
It is the first significant security incident since April 22, when 26 mainly Hindu civilians were killed at the tourist site of Pahalgam in Indian-administered Kashmir, triggering clashes with Pakistan.
"I assure everyone that the agencies will get to the bottom of the entire conspiracy," Modi said, in a speech during a state visit to neighbouring Bhutan, without giving further details.
"All those involved will be brought to justice."
At least 19 people were also wounded when flames ripped through several vehicles. Crime scene investigators scoured through the wreckage early on Tuesday.
The explosion on Monday came hours after Indian police said they had arrested a gang and seized explosive materials and assault rifles.
Police said the men were linked with Jaish-e-Mohammed, a Pakistan-based Islamist group, and Ansar Ghazwat-ul-Hind, a Kashmir offshoot of jihadist group Al-Qaeda.
Both groups are listed as terrorist organisations in India.
Defence Minister Rajnath Singh, speaking at a conference in New Delhi, said that investigative agencies were "conducting a swift and thorough inquiry" and that the findings "will soon be made public".
Singh, echoing Modi's words, said "those responsible for this tragedy will be brought to justice, and will not be spared under any circumstances."
Senior Delhi police officer Raja Banthia said they were investigating the blast in the crowded Old Delhi quarter of the city, under anti-terrorism laws.