At least nine people have been killed after a five-storey building being demolished in South Korea collapsed on to a bus.

As per National Fire Agency, debris from the collapsed building in the southern city of Gwangju fell on the bus that was carrying 17 people which had stopped on a nearby street.

Eight people sustained serious injuries in the collapse.

The reason for the collapse is not yet clear and search efforts are under way for survivors who may be trapped under the debris.

Videos uploaded to social media showed that the building collapsed directly on to the bus. Local media showed the debris falling on the bus and engulfing the street in a huge cloud of dust.

After the demolition of the building, a video surfaced showing dozens of rescue workers equipped with stretchers and crowbars searching for survivors while excavators hacked at a huge mountain of crumbled concrete and bent steel beams spilling over the motorway.

Fire officer Kim Seok-sun said in a televised briefing from the site that all workers on the site had evacuated before the building collapsed.

He further added that some of they had closed a pedestrian walkway near the building before the collapse.

In June 1995, one of the world's worst peacetime building collapses happened in South Korea, when Seoul's Sampoong Department Store collapsed, killing more than 500 people.