At least eight people were killed and more than 20 injured when a Hyundai i20 car exploded near Delhi's Red Fort on Monday evening.
The incident occurred around 18:52 local time as the slow-moving vehicle, carrying three occupants, stopped at a red light near a metro station.
The blast damaged nearby vehicles, including six cars and three autorickshaws, igniting fires and causing chaos in the congested old quarter.
Eyewitnesses described mangled wreckage, flames engulfing vehicles, and locals attempting rescues amid the devastation.
Delhi police are exploring all possibilities, with teams from the National Security Guard, National Investigation Agency, and forensic experts on site.
Home Minister Amit Shah, who visited the location and a nearby hospital, announced a thorough probe and a Tuesday morning meeting with senior officials.
Heavy security presence includes Uttar Pradesh Anti-Terrorist Squad, National Security Guard, and Central Reserve Police Force personnel.
Mumbai, Uttar Pradesh, and sites like Indira Gandhi International Airport have been placed on high alert, with enhanced protection at sensitive religious locations and border areas.
Prime Minister Narendra Modi extended condolences to victims' families and wished speedy recovery for the injured.
Opposition leader Rahul Gandhi called the news extremely heartbreaking.
The 17th-century Mughal fortress, a major tourist draw where prime ministers deliver Independence Day speeches, attracts thousands daily.
The explosion in this crowded, vulnerable area has raised concerns among residents and shattered the capital's recent calm.