A fire broke out on Friday at an oil refinery in the eastern South African city of Durban following an explosion, emergency responders said, adding that no-one was killed or hurt in the blast.

Smoke and flames billowed out of the refinery owned by oil company Engen in the Durban suburb of Wentworth early in the morning, prompting firefighters to rush to the site.

"Nobody was injured" in the "massive" blast, provincial emergency services spokesman Robert Mckenzie said via WhatsApp.

He added that a nearby block of flats also caught fire almost at the same time as the explosion.

Firefighters managed to extinguish most of the flames by mid-morning and bring both fires under control, while paramedics treated seven people for smoke inhalation.

Engen later confirmed that the fire started early on Friday morning and had since been "successfully extinguished".

The company said in a statement that the cause of the blaze was being investigated.

Engen's Durban refinery has a crude refining capacity of 120,000 barrels per day, according to the company's website.

An explosion in 2008 caused the plant to shut for around four months.

A fire also broke out the previous year when lighting struck a fuel storage tank, although the refinery remained operational after that incident.