The government of Equatorial Guinea said its forces have repelled an attack by gunmen on the country's presidential palace.
Officials said gunmen from southern Nigeria invaded the capital, Malabo, by boat on Tuesday.
Equatorial Guinea said the assailants were driven back, and that some of the gunmen were killed when the navy sank one of their vessels.
Witnesses reported hearing heavy gunfire and seeing goverment helicopters in the sky during the early morning battle. Malabo is now said to be calm, as soldiers patrol the streets.
President Teodoro Obiang Nguema was in the city of Bata at the time of the attack.
The government of Equatorial Guinea is blaming the attack on Nigeria's most prominent militant group, the Movement for the Emancipation of the Niger Delta. But in a statement sent to reporters, the group denied the allegation.
President Obiang has ruled Equatorial Guinea since 1979, when he seized power in a coup. The country is Africa's third biggest producer of crude oil.
Some information for this report was provided by AFP and Reuters.