Rebels in Ivory Coast have attacked French troops for a second time - just six days after a previous clash, a French army spokesman has said.

Around 30 insurgents ambushed a French patrol as it was leaving the town of Duekoue in the country's western cocoa belt on Friday, Lieutenant-Colonel Ange-Antoine Leccia told the BBC.

The French soldiers fired back but none was injured.

For three months the country has been racked by war between rebels and government forces.

The conflict has left hundreds dead and thousands homeless.

UN envoy

The United Nations Secretary General Kofi Annan appointed a "humanitarian envoy" to the former French colony on Friday.

Carolyn McAskie, a senior UN official, will be in charge of co-ordinating international assistance in the region.

French soldiers were originally sent to Ivory Coast to protect more than 20,000 French citizens living there.

But France increased its military presence after rebels took two strategic towns near the country's western border with Liberia.

French special troops at Duekoue also clashed with rebels last Saturday.

Reinforcements are expected to arrive from France on Saturday, making the force France's largest intervention force in Africa since the 1980s.

Plan disputed

Ivorian President Laurent Gbagbo has proposed a plan to end the conflict, but the BBC's Paul Welsh in Ivory Coast says it is unlikely to address the rebels' concerns.

The rebels want a change to the controversial system of deciding who is an Ivorian, which decides who can stand in elections or vote.

The president is suggesting a referendum which would decide who can stand for president, who can vote and who can own land.

But only those who are already Ivorians under the present system would be able to vote in the referendum - and that rules out most of the president's opponents.