More equipment is being mobilised to contain an oil spill from the ship Ultra Galaxy, which ran aground on South Africa's west coast and started to break up in stormy weather, authorities said on Monday.

Rough sea swells have battered the Panama-flagged general cargo vessel since it drifted onto a sand bank three weeks ago close to Doring Bay, some 300 km (186 miles) north of Cape Town, after the ship's crew abandoned the vessel when it started taking on water.

"Salvage operations are continuing and more equipment is being mobilized to contain the oil spill," said Tebogo Ramatjie, spokesperson for the South African Maritime Safety Authority (SAMSA).

The spill took place over the weekend when the ship broke into four sections, with large waves almost seven metres (23 ft) high crashing into the wreck every 15 seconds at one stage, SAMSA said.

An oil spill contingency plan was immediately launched and about 125 people from local communities are helping with mopping up operations, Ramatjie added.

The salvage team has managed to remove several lube oil drums and about eight tons of marine gas oil from the wreck's fuel tanks. SAMSA has said there were approximately 500 tons of fuel aboard the vessel that need to be removed.