Clashes were reported in Equatorial Guinea near the border with Cameroon, shortly after the West African state said it had thwarted a coup against President Teodoro Obiang Nguema, Africa's longest-serving leader.
Government troops had shot dead a "mercenary" and "used gunfire to disperse them in the forests along the border", state television TVGE said, without specifying how many "mercenaries" were involved or how long the clashes lasted.
Reports of the shooting came after Security Minister Nicolas Obama Nchama said in a statement on public radio that an attempted coup had been mounted on December 24, allegedly by foreign mercenaries recruited by political opponents.
"A group of Chadian, Sudanese and Centrafricans [citizens of the Central African Republic] infiltrated Kye Ossi, Ebibeyin, Mongomo, Bata and Malabo to attack the head of state, who was in the Koete Mongomo presidential palace for the year-end holiday," he said.
The "mercenaries... were recruited by Equatorial Guinean militants from certain radical opposition parties with the support of certain powers", the minister said.
The attempted infiltration had been repelled thanks to an operation carried out "in collaboration with the Cameroon security services", he said.
Sources told AFP that the country's ambassador to Chad had been arrested and was being held in a military camp.
Formerly a Spanish colony, Equatorial Guinea is one of sub-Sahara's biggest oil producers but a large proportion of its 1.2 million population lives in poverty.
Obiang, in power for more than 38 years, is accused by critics of brutal repression of opponents, electoral fraud and corruption.