Three people have been killed and three others injured in the South Korean capital, Seoul, after a decades-old overpass partially collapsed during a safety inspection on Tuesday, officials said.

The accident happened at 2.32pm when parts of the Seosomun overpass, located in western Seoul, collapsed during a safety inspection for the planned demolition of the overpass.

Television footage showed emergency workers conducting a search-and-rescue operation as a long segment of the structure lay collapsed on the street below, near a railway crossing in central Seoul.

Two men in their 50s and 60s were killed, while another injured victim was later pronounced dead.

Workers halted demolition work after noticing that part of the structure had slightly sunk while concrete slabs were being cut, said Lee Jong-woon, an official at Seoul’s Seodaemun District Fire Station.

The victims were crushed by debris and other wreckage after a section of the bridge deck suddenly collapsed, officials said.

All those killed and injured were senior city public works officials and a private-sector expert conducting the inspection, a fire official said.

Police and emergency officials sealed off traffic around the site, where twisted steel beams and shattered concrete slabs hung precariously from the edge of the overpass.

Some debris also fell on a nearby railway, forcing Korea Railroad Corp to suspend some services to Seoul Station.

The overpass had been scheduled to be demolished by early next month.

Built in 1966, the overpass had been undergoing demolition since August last year over safety concerns.