Islamabad, Pakistan (CNN) -- A suicide bomber in an explosive-laden car rammed into a police station building in Peshawar, Pakistan, on Wednesday, in a Taliban attack that killed four and injured 21 other people, a senior police official said.
The Pakistani Taliban said the attack was to avenge the killing of innocent civilians. The group's spokesman, Ihsan Ullah, told CNN on Wednesday that Pakistani security forces are carrying out those killings on the instruction of the United States in the name of a "war on terror."
Muhammad Ejaz Khan, the police official, said 13 civilians were wounded. The other eight were police.
Khan said several people were still under the debris. About 300 kilograms (661 pounds) of explosive material was used in a minitruck.
Fiaz Tooro, another senior police official of Peshawar, told CNN the building was being used as a Directorate of Counter-Terrorism to interrogate militants. No militants were being questioned or in the building at the time of the blast, he said.
The special police officials who were running the directorate were the target of the blast, Tooro said.
Journalist Amjid Afridi contributed to this report.