Intense fighting between the military and Islamist militants in north Nigeria is reported to have killed at least 185 civilians and destroyed 2,000 homes.Rocket-propelled grenades and heavy gunfire bombarded the remote town of Baga near the border with Chad for hours on Friday evening, government and military officials say.Nigeria faces a long-running insurgency in its predominantly Muslim north.The Boko Haram insurgency has left thousands of people dead since 2009.'Markets burnt'Residents of Baga fled into the bush and only returned on Sunday afternoon to find much of the town destroyed and human and animal corpses strewn through the streets.One local journalist said this marked a significant escalation in the insurgency in the area, with the militants using heavier weapons than in previous attacks.Residents said most of the bodies had been burned beyond recognition in blazes that had destroyed much of the town.One resident, Bashir Isa, told Associated Press: "Everyone has been in the bush since Friday night; we started returning to town because the governor came."To get food to eat in the town now is a problem because even the markets are burnt. We are still picking corpses of women and children in the bush and creeks.''Boko Haram wants to carve out an Islamic state across a swathe of Nigeria.Its name in the local Hausa language means: "Western education is forbidden".