A powerful car bomb exploded outside a KFC restaurant in the southern Pakistan city of Karachi on Tuesday, killing at least three people and injuring 15 others, police said. The blast struck at about 8:45 a.m., as commuters were heading to shops and offices in the crowded business hub, the scene of a number of bombings in recent months that have killed more than a dozen people. The restaurant, part of the global American fast food chain, was severely damaged and several cars on the street in front were overturned and set on fire. Mushtaq Shah, Karachi's police chief, told reporters the bomb was concealed in a car parked outside the restaurant. The blast killed three people and injured 15, Shah and other police officials said. Manzoor Mughal, a senior police investigator, said the blast left a two-meter (six-foot) crater and appeared to have been detonated by a timer. He said the KFC restaurant was the apparent target but refused to speculate on who might have carried out the attack. "We are trying to get information about that person who parked the explosive-laden car outside KFC," Mughal said. "We are also trying to trace the owner of the car." Mughal said the blast also damaged the offices of three Pakistani banks. There were no immediate claims of responsibility for the blast. Police said they tightened security in the city and were searching for clues about those behind the attack. Hundreds of people gathered at the bomb site in the area of government offices and luxury hotels. The blast was powerful enough to damage windowpanes at the Pearl Continental Hotel, which is popular with foreign tourists and businesspeople. A security guard in the hotel parking lot was hurt by a piece of flying metal, said a member of the hotel staff, Mohammed Arif. Karachi, Pakistan's largest city, is a center of Muslim insurgency, and previous bombings in the city have been linked to Islamic extremists opposed to Pakistani President Gen. Pervez Musharraf's close ties to the United States. Pakistan has been a key US ally in the struggle against Muslim extremists linked to al-Qaida and Afghanistan's former Taliban regime. Pakistan's information minister, Sheikh Rashid Ahmed, condemned the blast, calling it the work of the "enemies of Pakistan." The attack came three days before Pakistan is to host a conference of international donors to raise funds for victims of the devastating October 8 earthquake that killed about 86,000 people in the country's northwest and in Pakistani-controlled Kashmir. The KFC restaurant occupies the ground floor of a government office building housing the Pakistan Industrial Development Corp. Firefighters prevented the blaze from spreading to other parts of the building. Two bodies were pulled from the KFC restaurant while another man lay dead at the restaurant's entrance, witnesses said. The injured included security guards at the building and nearby banks. In September, bombs struck KFC and McDonalds restaurants in Karachi, injuring three people in attacks believed linked to a nationwide strike called by a hardline Islamic coalition opposed to Musharraf. A KFC restaurant in Karachi also was burned in May, killing six workers inside during an outbreak of religious violence between Sunni and Shiite Muslim groups in the city. Other violence in Karachi in recent years included two attacks against the U.S. Consulate and a May 8, 2002, car bombing in front of the city's Sheraton Hotel that killed 11 Frenchmen.