A homicide car bomber attacked a police station Saturday in northwest Pakistan, killing four people and wounding about two dozen, underscoring the continuing security threat to the country despite army operations against militants.

The blast also toppled a mosque next to the police station in Karak in North West Frontier Province, said Ajmal Khan, a government official. Both police and civilians were among the wounded.

The injured were transported to a nearby hospital where some were listed in critical condition. TV footage showed the charred skeleton of a vehicle and rescuers removing debris as they looked for survivors.

No one claimed responsibility, but militants have targeted police, security forces and government offices in various parts of Pakistan in recent years to avenge military operations in the country's tribal regions, which are close to Afghanistan.

Karak is near South Waziristan, a militant stronghold where the army launched a major offensive against militants in October. Although the government says the offensive has been completed, the army is still deployed there and conducting search operations.

A deadly wave of attacks hit Pakistan after the offensive began, claiming hundreds of lives. The militant campaign appears to have subsided somewhat, although last week teams of homicide bombers attacked two police stations in the northwestern district of Mansehra, killing an area police chief and wounding several officers.

Also Saturday, at least one person died and several others were wounded when gunmen opened fire on a procession in the northwestern town of Dera Ismail Khan, said Dr. Qutbuddin Khan, who works at a local hospital.

It was unclear who the attackers were. A local police official, Inyat Ullah, said officers were still investigating.

The procession was marking Mulid an-Nabi, the anniversary of the birth of Islam's Prophet Muhammad.