At least seven women workers have been killed after a fire broke out at a reportedly unlicensed garment factory in Shenzhen, southern China.

The fire, which was said to have been started by surplus material being burnt, also left four workers suffering from smoke inhalation.

According to local reports, the underwear factory's owner regularly locked doors and windows to stop workers from escaping.

Xinhua news agency said police were keeping the factory's owner, who employed 16 workers, under "surveillance".