The United States says it has launched its first unmanned Predator drone strike in Libya, while rebels say pro-government forces appear to be ending a siege on their key stronghold near Tripoli. A U.S. Defense Department statement said the airstrike was carried out today, but it did not say where the strike occurred. The strike is part of a NATO-led effort to impose a no-fly zone over Libya, where rebels are fighting to overthrow the government. The raid came less than two days after U.S. Defense Secretary Robert Gates said that President Barack Obama had approved the use of armed Predator drones in the military mission in Libya. In Misrata, which has seen some of the fiercest fighting of the conflict, rebels today were claiming victory as forces loyal to Libyan leader Moammar Gadhafi retreated. Yesterday, Libyan officials had said the military would withdraw from the city and leave its fate in the hands of the tribes around Misrata and the Misrata people. Earlier today, NATO forces bombed an area close to the Libyan leader's compound in Tripoli, hitting what reporters described as a military installation. There were no reports of injuries. The Italian Foreign Ministry said Libyan authorities had released an Italian ship detained in the port of Tripoli last month along with its 11 crew members. The ship, which was working for an Italian oil company, was seized shortly before the international coalition began imposing the no-fly zone.