A suicide attacker rammed a car packed with high-intensity explosives into a vehicle carrying an American diplomat Thursday, killing four people and wounding 52 outside the US consulate, ahead of this week's visit to Pakistan by US President George W. Bush, officials said. Bush condemned the attack and said "terrorists and killers" would not prevent him from coming to Pakistan on the final leg of a tour of South Asia. The blast ripped through a roadside parking lot of the Marriott Hotel, about 20 meters (yards) from the consulate gate, shattering windows at the consulate and on all 10 floors of the hotel. Ten cars were destroyed, and charred wreckage was flung as far as 200 meters (yards). "We have lost at least one US citizen in the bombing, a foreign service officer, and I send our country's deepest condolences to that person's loved ones and family," Bush said in neighboring in India. "Terrorists and killers are not going to prevent me from going to Pakistan." Initial investigations showed it was a suicide bombing in which the attacker had deliberately rammed his car into a vehicle carrying the American diplomat, blowing it into the air, across a concrete barrier and into the grounds of the hotel, a senior investigator and a counterterrorism official said on condition of anonymity because they were not authorized to make media statements. The driver of the diplomat's car, a Pakistani working for the consulate, also died. The other fatalities were a paramilitary guard and an unidentified woman. The body of a male victim, with part of its head missing, was flung by the blast onto the second story of the hotel's exterior. The attacker was also presumed killed in the attack, the two security officials said. His body was not recovered. The counterterrorism official said the attacker used high-intensity explosives and it was the most powerful blast he'd seen in Karachi - a hotbed of Islamic militancy. A Pakistani Foreign Ministry statement said the bombing was a "horrific terrorist attack" and it expressed "deep sadness" over the deaths of the American diplomat and his local driver. "This senseless act today further fortifies our resolve to fight terrorism," the statement said. "We all must work together to eliminate this terrible menace." Police initially said two car bombs had gone off, but provincial police chief Jahangir Mirza said that a single bomb may have triggered a second smaller explosion in a burning car. He said police were investigating whether it was a suicide attack. Some 52 people were injured, including a young Moroccan girl who was hit by debris, said provincial government spokesman Salahuddin Haider, adding investigators were trying to get video footage from surveillance cameras at the consulate. Nida Emmons, a spokeswoman for the U.S. embassy in Islamabad, confirmed an American and Pakistani employee of the consulate were killed, but wouldn't give their names. He said they were still investigating if any other consulate staff were hurt. The bombing left a crater two meters (8 feet) wide and more than 60 centimeters (2 feet) deep. The explosion propelled cars into the air and damaged other nearby buildings, including a naval hospital, and left the street strewn with mangled car parts. Mohammed Ali, who sells cigarettes nearby, said the first explosion occurred around 9 a.m., knocking him down and flattening his wooden stall. "Seconds later there was another explosion. We ran away to save our lives," said Ali. "The explosions set cars on fire and there was smoke all around ... I thought the explosions would burst my ear drums." Mohammed Jameel, a former army colonel, who was getting a medical checkup at the naval hospital, said the first explosion was "very intense" and the second one was smaller. "I saw two burning car seats land in the hospital lawn," he said. There was no immediate claim of responsibility for the blasts. But previous attacks against Westerners in Karachi have been blamed on the al-Qaida-linked Islamic militant groups. Several suspects have been convicted while some are still at large. Officials said the bombing could be timed for Bush's two-day visit to Pakistan. Bush was due in the Pakistani capital, Islamabad, which lies about 1,600 kilometers (1,000 miles) north of Karachi, on Friday, said an official on condition of anonymity because of the sensitivity of the trip. Bush's exact arrival time has not been officially announced. He made a surprise visit to Afghanistan on Wednesday before arriving in India for a scheduled trip. "All international media are eyeing Pakistan at this time, and terrorists are using this to defame Pakistan and Muslims," Ishratul Ibab, the provincial governor, said. Islamic militants who have targeted the US Consulate in Karachi, Pakistan's largest city, before. In June 2002 a car bombing attack left 14 people dead, all Pakistanis outside the building, which lies in an upscale district of the sprawling city's downtown. In March 2004 police defused a huge bomb less than five minutes before it was timed to explode outside the consulate. The bomb was packed in a small van that was parked on a street near the building. Marriott Hotel deputy manager Shahzad Ashif said windows were broken on all 10 floors and balcony door latches were blown in on the first two floors but none of the guests inside were injured. The hotel was being evacuated and guests moved to other hotels, he said. A group of about 16 Western guests at the hotel were gathered in a ground floor restaurant after the blasts and were making calls from their cell phones. None appeared hurt.