Officials in northwest Pakistan say a suicide car bomber has rammed his vehicle into a U.S. government car in Peshawar, killing four people, including two Americans. Several people were wounded in the huge blast.

Monday's explosion happened in an area of Peshawar that is home to several foreign aid organizations and the United Nations.

The bomber struck the vehicle after it left the U.S. consulate.

There is no immediate claim of responsibility for the attack.