ISLAMABAD, Sept. 6 (Xinhua) -- At least 25 policemen are still being trapped under the debris of a building damaged by a suicide car bomb attack that occurred early Monday morning targetting a police station in Lakki Marwat in Pakistan's northwest province of Khyber Pakhtunkhwa, said police sources.

Early monday morning, an explosive-laden vehicle rammed into the rear wall of a police station in the city, which reportedly was housing an estimated 40 to 50 policemen at the time, killing at least 14 people and injuring more than 40 others.

Most of the killed were policemen and the killed people also included four girls, said hospital sources, adding that some of the injured people are in critical condition.

The blast also caused a serious damage to some nearby buildings close to the police station.

So far no group has claimed the responsibility for Monday's attack which coincided with the Defense Day of Pakistan, which is designed to celebrate the victory of Pakistan over India in 1965 war.

Eyewitnesses said that police have quickly cordoned off the blast area following the attack and a search operation was launched in the nearby areas.

While most of the injured people have been shifted to nearby hospitals, rescue workers are still working on the site trying to pull out the people trapped in the debris of the damaged buildings.

Police said that the attacker whose identity is yet to be found chose the rear wall of the police station as the target due to the fact that the front and side walls of the police station were heavily guarded.

Monday's suicide blast is the third most serious of its kind that occurred in Pakistan since the beginning of this month. On Sept. 1, a triple-blast, two of which have been determined to be of suicide nature, in Pakistan's eastern city of Lahore, killed 37 people and injured more than 200 others. On Sept. 3, a suicide bomber attacked a rally in the country's southwestern city of Quetta, killing about 70 people and injuring more than 160 others.