ABIDJAN, Ivory Coast: A United Nations helicopter fired at strongman Laurent Gbagbo's forces Monday as France authorized its military to take out his heavy weapons, an unprecedented escalation in the international community's efforts to oust the entrenched leader. The office of French President Nicolas Sarkozy said UN Secretary General Ban Ki-moon had requested France's military participation. Gbagbo lost presidential elections in November but has refused to cede power to Alassane Ouattara even as his West African nation teetered on the brink of all-out civil war. Forces backing Ouattara launched a dramatic offensive last week, seizing control of the administrative capital and other towns before heading toward Abidjan. Monday, the UN helicopter fired on Gbagbo's troops at about 5 P.M. local time (1700 GMT) to prevent them from using heavy weapons at the Akouedo camp in Abidjan, said Nick Birnback, the spokesman for the UN Department of Peacekeeping Operations. Meanwhile, fighters backing Ouattara entered Abidjan by the truckload Monday afternoon as part of a final offensive to take the last piece of the West African country still largely controlled by Gbagbo.