A building in an old quarter of New Delhi collapsed Tuesday night, killing at least five people and injuring 25, police said.

Many of those hurt are said to be in critical condition, and 20 people are believed to be trapped inside the building, police said. An adjacent building has been evacuated in fear of a similar collapse, a Reuters photographer at the site said.

Television images showed fire engines and ambulances rushing to the spot in Chandni Chowk, a Mughal-era walled city.

Telecoms Minister Minister Kapil Sibal was blocked by an angry mob from entering a local hospital where the injured have been admitted, TV channels said.

NDTV, citing police, said the building collapsed because of pressure from adjacent construction work.

Many Indian buildings do not conform to safety regulations, with owners building extra floors or structures without approval.

In November last year, a five-story residential building collapsed in the capital, crushing at least 60 people to death.