Heavy gunfire and explosions rocked Samarra on Friday after U.S. and Iraqi forces launched a major assault to retake control of the insurgent stronghold north of the capital. Hospital officials said more than 80 people were killed and 100 wounded. Troops of the U.S. 1st Infantry Division, Iraqi National Guard and Iraqi Army moved into Samarra after midnight under cover of heavy fire, securing government and police buildings early Friday, the U.S. command said. Residents cowered in their homes as tanks and warplanes pounded the city overnight. The sound of loud shelling mixed with the crackle of automatic gunfire continued into the morning. At least three houses were flattened and dozens of cars charred, residents said.