Baghdad, June 10 : At least three Katyusha rockets struck an Iraqi military airbase in Salahudin province, a security source said. The incident took place on Wednesday evening when the rockets landed on the Balad Air Base, some 90 km north of Baghdad, without immediate reports about the casualties, Mohammed al-Bazi, from the provincial police, told Xinhua news agency. Two of the rockets hit a building inside the airbase, leaving minor damages, al-Bazi said, adding that the rockets were fired from the neighbouring province of Diyala. Balad, which houses Iraqi F-16 fighters and a camp for some US experts for the jets, is the largest military airbase in Iraq. The US troops and experts withdrew previously from the airbase after their camp came under a series of rocket attacks by unidentified militias. However, Tahseen al-Khafaji, spokesman of the Iraqi Joint Operations Command, told the official Iraqi News Agency that the international coalition has begun providing spare parts for the F-16 and other aircraft, as part of the coalition's support for the Iraqi security forces. No group has so far claimed responsibility for the attack. The Iraqi military bases housing US troops across Iraq, as well as the American embassy in the Green Zone, have been frequently targeted by mortar and rocket attacks. /IANS