At least 20 young people were found dead at a nightclub in a township in South Africa's southern city of East London on Sunday, police said.

"We got a report about 20 (people) that died in a local tavern in Scenery Park which is based in East London," a provincial police chief brigadier Thembinkosi Kinana told AFP.

"We are still investigating the circumstances surrounding the incident," he added.

He said the victims were aged between 18 and 20 years.

Unverified pictures shared on social media showed bodies with no visible signs of injuries, strewn on the floor of the club.

Local television showed police officers trying to calm down a crowd of people gathered outside the club in the city, which lies on the Indian Ocean coast, nearly 1,000 kilometres (620 miles) south of Johannesburg.