A car filled with explosives rammed into a US government vehicle in the north-western Pakistani city of Peshawar, killing two people and wounding 19 others, according to police.
The identities of those who died in the attack were unclear, said local police officer Pervez Khan, but he added that some of the wounded were foreigners.
A US passport was found in the wreckage, said another police officer, Javed Khan. The US embassy in Islamabad said it was investigating the report.
Peshawar is located near Pakistan's semi-autonomous tribal region, the main sanctuary for Taliban and al-Qaida militants in the country. The city has been hit by scores of bombings in recent years, but attacks against US targets are relatively rare.