It brings the nation a step closer to its aim of developing a compact nuclear device to arm missiles.

The explosion took place this morning at Reggan in south-western Algeria, according to a communique from the French Armed Forces Ministry.

France's first two atomic bombs were also exploded there earlier this year - in February and April .

The communique stated the "nuclear explosion of limited power" had been successful and that care had been taken to prevent radioactive fall-out from affecting people living in the remote part of the desert, and those in neighbouring African countries.

Japan protests

The test provoked swift condemnation from Japan, which has also protested in the past against tests carried out by the United States, Britain and the USSR. All three nations agreed two years ago to cease test explosions but France would not be bound by such an agreement.

Today, Moscow joined Japan in condemning the test saying it was a serious blow to any hope of disarmament and against the wishes of the United Nations. Moscow Radio described the act as "a monstrous challenge to world public opinion".

Egypt, Morocco, Nigeria and Ghana have also expressed outrage at France's action and its timing - on the eve of the African summit in Casablanca.

In Cairo, the deputy secretary general of the Arab League, El Dardiri Ismail, called for all Arab nations to break off political and economic links with France.

Today's bomb contained plutonium and had an explosive force equal to 10,000 to 14,000 tons of TNT - half as powerful as the Hiroshima bomb.

It was exploded at the top of a steel tower. Military equipment, dummies and caged rats and mice were positioned in the area of the blast were monitored during and after the explosion.

The rodents have been flown to Paris for examination.

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