Some attempted migrants have been jailed in Mauritania

The offer comes after a Spanish hospital ship recovered the bodies of around 18 Africans in the sea 400 miles (640km) south of the Canary Islands.

Earlier, around 400 Africans were found in boats trying to reach the islands.

Spanish police fear thousands of people are gathering in Mauritania and the Western Sahara to try to make the trip.

The region appears to be the new launching point for those attempting to reach European shores since security has been stepped up in Morocco and the Straits of Gibraltar.

The bodies were picked up by the Spanish ship Esperanza del Mar (Hope of the Sea) after they were discovered by a fishing boat.

Hundreds of would-be African immigrants, packed into boats, have been picked up in recent weeks as they have tried to reach the Canary Islands.

Fatal seas

Earlier this month 45 drowned in separate incidents after leaving the African coast. Since 10 November 2005, at least 1,200 people have died trying to make the trip, the Mauritanian Red Crescent says.

Spanish ministers decided to launch a number of measures to try to combat the problem during an emergency meeting on Wednesday.

As well as patrol boats, they will offer Mauritania help in setting up reception centres for illegal immigrants, which could be run by non-governmental organisations.

They will also respond to a request for further help from the Canary Islands to deal with the situation, such as increasing coastal patrols.

The BBC's Danny Wood says that as reception centres in the Canary Islands overflow, Spain's army is making military barracks available for the new arrivals.