At least 15 people have been killed in an attack on the Ivory Coast's armed forces in the country's southwest, according to state television.

The state-run RTI network said on Saturday the attack happened overnight on Thursday and it appeared the assailants had come across the Liberian border into the Tai region of Ivory Coast.

The attack caught the soldiers by surprise, RTI reported.

"Members of the FRCI [Republican Forces of Ivory Coast] were attacked by surprise. The toll from the attack was 15 dead," RTI said, adding that reinforcements were being sent to the porous and densely forested border region.

Ivorian forces attacked on Liberia-Ivory Coast border

Leon Alla Kouakou, the Ivorian military spokesman, confirmed there had been an attack in Tai, but did not provide details.

In July, West African leaders urged the United Nations and ECOWAS, the regional bloc, to step up monitoring
of the Liberia-Ivory Coast border after signs that mercenaries had been operating there since April.
   
The leaders of Guinea, Ivory Coast, Liberia, and Sierra Leone said at the time that insecurity on the
Liberia-Ivory Coast border represented a threat to the entire West African region.   
   
The government has said Liberian mercenaries were
hired by supporters of Laurent Gbagbo, a former president, during the four-month post-election conflict which ended with his capture and arrest in April.
   
The FRCI was the name given to forces that battled to remove Gbagbo and allow Alassane Ouattara, the current president of the Ivory Coast, to assume power after winning last November's presidential election.

Gbagbo disputed the election result, sparking the conflict.