Rebels in Ivory Coast say they may launch a full-scale assault after the government broke a cease-fire by attacking a rebel-held village.
Meanwhile, the government accuses Liberian fighters allied to the rebels of going on a looting rampage in the west.
An Ivorian government spokesman accuses Liberian fighters of rampaging through the village of Neka, in western Ivory Coast.
Residents of nearby towns say the attackers apparently crossed over the border from Liberia, and hundreds of people are fleeing the area. The rebels claim they are moving south toward the port city of Tabou.
A government spokesman says Liberian fighters went on a looting rampage in the village, raping and killing civilians. The Reuters news agency quotes refugees as saying they saw "lots of bodies" as they fled the town.
There have been previous reports of Liberians fighting with the western rebels, and of looting in other towns when the western factions have taken over.
Western rebels claim to have captured the town without a fight Wednesday. Rebel leader Felix Doh says government loyalist troops in the village switched sides and handed it over to his forces.
The rebels' move on Neka has opened a new front in an increasingly complex civil war. Government troops and helicopter gunships have been seen heading west toward the area.
Meanwhile, a different rebel faction in northern Ivory Coast has indicated Wednesday's government attack on a rebel-held village has voided the cease-fire signed in October. He rebel leader Guillaume Soro said his forces now have what he called "a free hand" to launch a general offensive.
French peacekeepers say a government helicopter killed 12 civilians Wednesday when it attacked the fishing village of Menakro, not far from the rebel stronghold of Bouake in central Ivory Coast. Witnesses say a Russian-made helicopter piloted by white mercenaries fired rockets and heavy guns at the village.
An Ivorian government spokesman says the attack was aimed at military targets, not civilian ones, and it came after loyalist troops were attacked by rebels nearby.
The Ivorian government and the northern rebel group, known as the Patriotic Movement of Ivory Coast, signed a cease-fire in October at peace talks in Togo. The other two rebel factions have not signed the cease-fire.
France has strongly condemned the attack. A French spokesman in Paris said any violation of the cease-fire is unacceptable.
France has sent roughly 2,500 troops to Ivory Coast to enforce the shaky cease-fire in the former French colony.
The French foreign minister is expected to arrive in Ivory Coast Friday for talks with both government and rebel leaders.
Peacekeepers from other West African nations are also due to start arriving in Ivory Coast Friday.