At least 109 insurgents and one American soldier were killed overnight in a major offensive launched by U.S. and Iraqi forces in the city of Samarra, U.S. military officials said Friday. In the largest operation seen in Iraq's Sunni Triangle city in months, an estimated 3,000 U.S. troops moved into Samarra late Thursday. It was a response to what the United States called "repeated and unprovoked attacks by anti-Iraqi forces." "This, they say, is the definitive battle for Samarra," CNN Correspondent Jane Arraf said amid heavy fire Friday morning as she traveled with the U.S. Army's 1st Infantry Division. Dr. Khalid Ahmed said at least 80 bodies and more than 100 wounded were brought to Samarra General Hospital, but it was not immediately clear how many were insurgents. The hospital was running out of supplies, Ahmed said.Also Friday, U.S. warplanes and tanks attacked the vast Baghdad slum of Sadr City, The Associated Press reported. "We will spare no effort to clean all the Iraqi lands and cities from these criminals and we will pave the way through these operations not only for the reconstruction but also for the general elections," said Qasim Dowoud, minister of state for national security, according to the AP.