Two people have died after a car filled with explosives rammed into a US government vehicle in the north-western Pakistani city of Peshawar, police said.
The dead were from Pakistan, while two foreigners were among the 19 people wounded in the attack, senior police officer Javed Khan said.
Their nationalities were not immediately known, but a US passport was found in the wreckage of the vehicle that was attacked, he said. The US embassy in Islamabad said it is investigating the incident.
Peshawar is located near Pakistan's semi-autonomous tribal region, the main sanctuary for Taliban and al Qaida militants in the country.
The vehicle was attacked after it left the US consulate in Peshawar and was travelling through an area of the city that hosts various international organisations, including the United Nations, said police officer Pervez Khan, who was part of the security escort for the vehicle as it moved.
Local TV footage showed an SUV at the site that was completely destroyed. Mr Khan said the images were of the US vehicle that was attacked.
A police explosives expert, Abdul Haq, said 240lbs of explosives was used in the attack.
US Secretary of State Hillary Rodham Clinton, on an Asian tour, condemned the suicide bomber for ramming his car into a US government vehicle, injuring two Americans.
Mrs Clinton, in the midst of an Asian tour, said at the outset of a news conference in Jakarta that she wants to "very clearly condemn the attack on our consulate personnel in Peshawar, Pakistan."
Mrs Clinton added: "We pray for the safe recovery of both American and Pakistani victims and once again we deplore the cowardly act of suicide bombing and terrorism that has affected so many around the world."