A man has been arrested on suspicion of setting fire to clothing inside a Decathlon store in Hong Kong, injuring a shop worker who tried to put out the flames.

Police said the incident was reported at about 3pm at the Telford Plaza store on Wai Yip Street in Kowloon Bay, where the suspect allegedly set fire to some shirts before fleeing.

A 22-year-old male staff member suffered slight burns to his hands while trying to extinguish the flames and was taken to United Christian Hospital in Kwun Tong.

Firefighters quickly put out the fire, which caused HK$1,032 (US$132) worth of damage.

The suspect, described as about 1.7 metres (5 feet, 6 inches) tall and of heavy build, wearing a khaki top, blue trousers and a cap, was later traced to Ying Shun House in nearby Choi Ying Estate, where officers arrested the 40-year-old man at about 5pm.

A police source said the man has a mild intellectual impairment and holds a disability certificate. The case has been classified as arson, with the motive still under investigation.