Morocco has launched an operation to empty an oil tanker that ran aground during a storm near the southern port of Tan Tan with 5,000 tonnes of fuel on board, an official said.

The fuel was being pumped into trucks, with the operation to last between five and seven days depending on the weather, M'Hammed Atmani, police chief at the national ports agency, was quoted as saying by the official MAP news agency late on Tuesday.

The ship was travelling from the Canary Islands when it ran aground last week, with heavy waves dragging it towards a rocky area, sparking fears of an oil slick on Morocco's Atlantic coast.

No major leaks from the ship have been reported, with a source at the environment ministry saying the cold sea temperatures had thickened the fuel, reducing the risk of any leakage.

Rabat had dispatched tug boats and appealed to Spain for assistance in refloating the tanker, but the rescue efforts were unsuccessful.

The fuel was being transported to a power station in Tan Tan, which lies close to the Western Sahara, around 300 kilometres (190 miles) south of the Moroccan resort town of Agadir.