At least five people have been killed and 25 others wounded in an attack on the police headquarters in the eastern Pakistani city of Lahore, police officials and medical sources say.

A suicide bomber approached the entrance of the building, and on being denied entry, detonated his explosives, senior police official Haider Ashraf told Al Jazeera.

Earlier accounts of emergency services said at least eight people were killed in the blast.

The attack took place just past 1:00pm local time on Tuesday, and the force of the explosion shattered the windows of several adjacent buildings.

Plumes of smoke were seen rising across the area, as several nearby vehicles and a building caught fire after the explosion in the city’s old quarter.

"It appears to be a suicide bomber who approached the Police Lines and exploded himself when he was denied entry," Ashraf told Al Jazeera.

Amin Wains, Lahore's police chief, confirmed that account while speaking to reporters at the site of the blast.

"We had made full [security] arrangements, and that is why they were not able to enter the police lines area," Wains told reporters.

The injured were taken to the nearby Mayo and Ganga Ram hospitals, as rescue services worked to put out the flames from the explosion.

Several important government buildings are located near the police headquarters, including the provincial assembly and the Governor House for Punjab.

Taliban claims responsibility

The Tehreek-e-Taliban Pakistan's breakaway Jamaat-ur-Ahrar faction claimed responsibility for the attack, in a statement emailed to Al Jazeera.

"We make it clear to these rulers that we will take revenge for the spilling of innocent Muslims' blood. Wait for us, our operations will continue until an Islamic system is put into place," TTP-JA spokesperson Ehsanullah Ehsan said.

The explosion in Lahore comes just days after several suicide bombers targeted a Shia mosque in the northwestern city of Peshawar, killing at least 20 people.

Lahore, the political stronghold of Prime Minister Nawaz Sharif, was last witness to such an attack when the Wagah border post was the site of an explosion on November 2. At least 60 people were killed in that attack.

Tuesday’s blast marks the fourth major attack since the government launched a renewed crackdown on armed anti-State groups following the December 16 attack on a Peshawar school, which killed more than 140 people and was the deadliest such attack in Pakistan’s history.