"Two of the injured are in a serious condition" while some workers had been discharged after first aid, he added.

The New Delhi metro system, launched in 2002, has been lauded for its cleanliness and efficiency and has revolutionised travel in the city.

Sunday's accident is the second major incident involving the Delhi metro service in less than a year.

In October, two people were crushed to death and 12 injured when a bridge being built to extend the metro system collapsed onto a bus and cars.