MADRID, Aug 26 (Reuters) - A group of African migrants rescued off Spain's coast said they had to throw the bodies of 25 companions overboard as their overcrowded boat drifted for days in the Mediterranean, government officials said on Tuesday.

A container ship found 25 people aboard the half submerged inflatable dinghy on Monday and took them to the southern Spanish port of Malaga.

The migrants said 50 people were originally aboard the boat and officials are checking the information.

Four of the migrants were thought to be children and three of the 25 survivors required medical attention, officials said.

Dozens of African migrants have died in recent months as they tried to take advantage of calmer summer seas to make perilous voyages to Spain's Canary Islands and mainland in search of jobs and a better life in Europe.

Tens of thousands have made it to Spanish shores in recent years, prompting Spain's Socialist government to toughen its line on illegal immigration. Many thousands more are believed to have drowned or died of thirst or exposure in the attempt.

The number of arrivals has more than halved since 2006, when 30,000 Africans managed to make it to the Canary Islands, pushing immigration to the top of Spanish political concerns.

In response, the Spanish government promised to repatriate all illegal migrants. It also set up joint naval patrols with European partners and reached agreements with African countries to prevent their citizens trying to leave. (Reporting by Raquel Castillo; Writing by Andrew Hay; Editing by Richard Williams)

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