* Local residents flee nearby areas
* Raid follows several attacks last week
* Authorities blamed pro-Gbagbo militias for Abidjan attacks
By Joe Bavier
ABIDJAN, Aug 13 (Reuters) - Gunmen attacked a border post on Ivory Coast's volatile western frontier with Liberia on Monday, the latest in a series of raids on police and army installations, the United Nations mission in the country and local residents said.
Authorities in the world's top cocoa grower have blamed militias still loyal to former president Laurent Gbagbo for attacks in the capital Abidjan last week that killed at least 10 soldiers and heightened fears of renewed instability.
Residents in the town of Toulepleu began hearing distant gunfire and explosions on Monday morning, and exchanges of fire continued into the early evening.
"There was an attack, yes...There have been population movements. We have peacekeepers in Toulepleu, but it was some distance from them," said Kenneth Blackman, spokesman for the U.N. mission known as UNOCI.
There were no confirmed reports of casualties and Ivorian military and government officials were not immediately reachable for comment.
"The situation is very confused. We know the border post was attacked. We are hearing the shooting. We don't know who attacked," said one Toulepleu resident who asked not to be named. "Two-thirds of the people here in town have fled. The others are staying inside," he added.
A Liberian defence official, speaking to Reuters on condition of anonymity, said soldiers were being sent to the area of the clashes to help contain the violence.
"The ministry ... has dispatched military officers to the border line to remain at our side to protect it. These are all precautionary measures being taken by our government," he said.
More than 20 people, including seven U.N. peacekeepers, were killed in raids further south on the Ivorian side of the border in June. Ivory Coast blamed the attacks on pro-Gbagbo militias and mercenaries who fled into Liberia at the end of a brief civil war last year.
Some 3,000 people died in that conflict, which erupted after Gbagbo refused to accept the victory of rival Alassane Ouattara in an election held in late 2010.
Gbagbo was captured during the battle for Abidjan in April last year and is now in The Hague awaiting trial before the International Criminal Court on war crimes charges.
Ouattara's government has said the continuing violence is the work of fighters trying to create insecurity and scare off investors, who are beginning to trickle into the country, once an economic motor of French-speaking West Africa.
Last week the interior minister announced that 11 men, including serving military personnel, had been arrested for alleged involvement in the attacks in Abidjan.
Gbagbo's political allies have rejected accusations of involvement in the violence and accuse the security services of widespread round-ups of suspected supporters of the former president. (Additional reporting by Alphonso Toweh in Monrovia, editing by Tim Pearce)