The blast hit at an abandoned plastics plant in Qixia district early in the morning of July 28, Xinhua news agency said.

Buildings and vehicles within 100m of the factory suffered severe damage. The injured included passengers on a bus that was passing at the time.

The blast was caused by a leak from a gas pipeline inside the factory, media reports said.

Five of the dead were reported to have been killed immediately.

At least 15 other people were seriously injured and more than 100 people were taken to hospital, the news agency said.

A doctor at Nanjing's Zhongda hospital said that hospitals across the city were treating the injured, most of whom had burns.

The State Administration of Work Safety said the blast happened after workers dismantling the plant damaged a propylene pipeline. The leaked gas was then ignited when a car engine was started at the scene.