A large fire ripped through the 139-year-old Grey Street Mosque in South Africa's southeastern port city of Durban Monday, emergency services and religious leaders said.

The blaze at the mosque, one of the largest in the southern hemisphere, also damaged three adjacent buildings in the city's central business district, emergency services spokesman Robert Mckenzie told AFP.

Videos posted on Twitter showed crowds looking on as curtains of flame raged through the upper floor of the building.

Firefighters managed to bring the fire under control in about two hours, before it reached the prayer area on the ground floor.

The cause of the fire was not immediately clear, but South African Muslim Network (SAMNET) chairman Faisal Suliman said it was believed to have started in one of seven staff flats located above the mosque and may have been caused by an electrical fault.

"It's presumed to have been accidental, and not to have been any foul play," Suliman told AFP.

Mosque workers and their families were all evacuated before the fire spread and there were no injuries reported.

The mosque is a landmark of Durban city centre and a well-attended house of worship with Suliman saying it offers space for up to 7,000 at prayer.

As well as hosting Friday prayers, it has been visited by prominent figures including South Africa's late first Black president Nelson Mandela, British musician Cat Stevens and former heavyweight boxing champion Muhammad Ali.