A four-year-old boy has died after being wedged under an escalator handrail at a Chinese subway station.

The boy fell under the handrail while playing with it unsupervised in the Chinese city of Chongqing on Thursday.

The escalator, in Chongqing's Hongqiaohegou subway station, remained running for 20 seconds until it was switched off by station staff, according to local media reported by the South China Morning Post.

Local rail authorities said a woman left her four-year-old son and three-year-old daughter unsupervised in the station’s ticketing hall.

The boy fell while playing with the handrail, trapping his chest between the bottom of the handrail and the ground.

Chongquing Rail Transport released a statement on its Weibo account saying tit is investigating the incident.

The statement, reported by the BBC, said: “We are deeply regretful and heartbroken over this case. We also would like to remind all passengers to look after their young children and old folks when travelling, be more alert, and avoid similar accidents.”

The incident follows a slew of recent accidents involving escalators in the country, prompting nationwide safety concerns.

In July, a 30-year-old woman was killed after falling through an escalator floor plate at a shopping mall in southern Hubei.

Xiang Liujuan, who was with her two-year-old son at the time, managed to push him to safety before being dragged into the machinery.

A week later a shopping mall cleaner was forced to have his foot amputated after trapping it in an shopping mall escalator in Shanghai.

37 people were killed in China in escalator accidents last year, according to the South China Morning Post.