A partially built flyover collapsed in the eastern Indian city of Kolkata on Thursday, killing at least one person and injuring scores, with many more feared trapped under mounds of debris, an official and a lawmaker said.

Police and passers-by were using their hands to try to move giant slabs of concrete and metal to reach those trapped, after the bridge collapsed at around lunchtime on a busy road, television footage showed.

"One person is confirmed dead. Sixty-two people who were trapped under the debris have been shifted to hospital, some of them are critical," Anurag Gupta, National Disaster Management Authority spokesman, told AFP.