Three people were killed and at least 27 others were injured after an explosion ripped through a small hotel in the port of city of Zamboanga on Mindanao island, southern Philippines, Sunday night. Reports said most of the casualties were at the hotel to celebrate a local wedding. The force of the blast destroyed the upper floor of the two-storey building, while a fire that followed the explosion quickly razed the ground floor. "The bomb is composed of TNT component, we are looking the Abu Sayyaf terrorist group behind this explosion," Regional police director Felicisimo Khu said. Initial investigations showed the explosion was likely caused by an improvised bomb, although no group had yet claimed responsibility for the attack. Officials blamed the Abu Sayyaf group - a small militant organisation with links to al-Qaeda. The southern Philippines suffers from several overlapping conflicts. Abu Sayyaf is a small, violent group which has launched several large-scale attacks in the past. The city of Zamboanga has been the target of frequent bomb attacks, often carried out by extremists and armed gangs operating in surrounding areas or nearby islands. In late-October, a bomb killed two people in a roadside eatery in Zamboanga.