The Ivorian army says it has attacked rebel positions in western Ivory Coast following clashes in that region earlier Monday, while supporters of President Laurent Gbagbo have set up barricades in many parts of the commercial capital Abidjan. The events mark one of the most serious challenges to the stalled peace process.

Speaking on state television late Monday, army spokesman Jules Yao Yao said combat helicopters bombarded rebel positions, destroying five armored vehicles and killing many rebels.

A rebel spokesman, Sidiki Konate, confirmed the bombardments took place, but said the attacks targeted unarmed rebels who were retreating.

Mr. Konate says the violence was provoked earlier in the day, when unidentified assailants posing as rebels, attacked the western town of Gohitafla.

Authorities in Abidjan blamed what they called dissident rebels.

Meanwhile in the commercial capital, supporters of President Laurent Gbagbo set up barricades throughout the night, blocking and searching vehicles. Many of them, like this unemployed woman who says her name is Maya, said they were trying to kill white people.

She says each Ivorian should kill one French person. Supporters of Mr. Gbagbo have accused the former colonial power France and its French peacekeeping troops now deployed in Ivory Coast of favoring the rebels.

Protests started Monday with pro-Gbabo protesters hurling stones and burning tires in front of the French embassy. Demonstrators also vandalized 30 vehicles belonging to the U.N. peacekeeping mission.

Members of a group called the Young Patriots said they would attack French interests in Abidjan on Tuesday, prompting French schools to close for the day.

The American embassy also said it would be closed.

The escalating tensions come as President Gbagbo is outside the country. A top presidential aide said Mr. Gbagbo was in London Monday night on his way to the United States for a private visit.

Northern-based rebels have refused to disarm, accusing Mr. Gbagbo of blocking implementation of the power-sharing peace deal signed in January 2003.