Suspected al-Qaida-linked militants bombed a Roman Catholic cathedral compound and a building housing a government office Sunday in the southern Philippines, police said. No one was injured in the blasts. Police have been placed on the highest level of security following the dawn explosions in Zamboanga city, regional police Chief Superintendent Jaime Caringal said. Government troops and police had already tightened security in the town for a weeklong national sports festival and a medical conference, he said. Zamboanga, about 860 kilometers south of Manila, is home to US troops providing counterterrorism training to Filipino soldiers. The military says the region is home to more than 300 armed members of the al-Qaida-linked Abu Sayyaf terror group. Caringal said a mortar round, concealed in a box, exploded under a car in the parking lot of the Immaculate Conception Cathedral, damaging two cars, a concrete wall and two steel gates.