YAOUNDE (AFP) -- 21 Cameroonian soldiers were killed and six injured in an attack by Nigerian rebels in the Bakassi peninsula, Cameroon military sources said Tuesday.

The long-disputed peninsula was officially handed over to Cameroon by Nigeria in August 2006, in line with a ruling by the International Court of Justice to settle the territorial row.
""There was an attack by pirate Nigerian rebels Monday afternoon against a Cameroonian military position designated as a 'group operational center' in Bakassi,"" the source told AFP in Libreville by telephone from Gambon.
Two of those killed were officers, she added.
The attackers left shortly after the incident and calm has returned to the area Tuesday, the source said.
A source at the Cameroon Defense Ministry in the capital Yaounde said the army had had ""serious problems"" in the area but refused to eludicate further.
La Nouvelle Expression -- a Cameroonian newspaper -- said on Tuesday the attack was carried out by armed men ""disguised as pirates"", intent on seizing Cameroonian army weapons from the base.
The Cameroonian army was taken by surprise by the attack, the military source told AFP, because it assumed the boats were carrying ordinary citizens, and respected their right to travel freely -- until at the last moment they spotted the passengers were armed.
The attackers were not operating under Nigerian authority, the source clarified.
The disputed 1,000 square kilometer (620 square mile) Bakassi peninsula is potentially rich in oil.