Islamabad  - Pakistani commandos killed four militants and arrested three others Monday, ending an eight-hour standoff at a police-training academy in the eastern province of Punjab that left several police dead and around 100 wounded, officials said.

An armed group carrying assault rifles, grenades and explosives attacked the sprawling police-training school in the Manawan area in the outskirts of the provincial capital of Lahore during the morning drill.

Television footage showed police officers celebrating the retaking of the facility on its rooftop by firing their rifles in the air and yelling, "God is Great."

"The operation is over," said Rehman Malik, security adviser to the prime minister. "Four terrorists were shot dead by the security forces and three arrested," he told reporters.

Private television channels reported that three militants actually detonated explosive vests they were wearing while military commandos were clearing rooms of the three-storey building.

There were conflicting official claims about the death toll. While citing police sources, the Urdu-language news channel Geo said 27 policemen, mostly raw recruits, were killed and more than 90 injured.

The provincial Home Secretary, Rao Iftikhar Ahmed, told the German Press Agency dpa that eight attackers were killed, adding the death toll might rise as some bodies were still lying in the building.

A second police official said eight police recruits and four civilians, including a woman, died in the assault.

According to Malik, details were being collected to ascertain the number of casualties.

The militants, some in police uniforms, attacked the training school by first lobbing hand grenades over the perimeter wall and then opening indiscriminate fire on the panicked law enforcement officers.

Salman Taseer, the governor of Punjab, said eight to 10 terrorists attacked the academy. "They were wearing masks and plainclothes when they raided the centre," Taseer told reporters.

Several policemen were seen lying motionless in pools of blood on the parade grounds immediately after the beginning of the raid.

A senior police officer, Mushtaq Sukhera, said around 850 recruits were normally trained here "but we don't know exactly how many were inside when the attack took place." But the actual numbers of the hostages were not clear.

Civilians gathered outside the training school chanted slogans of "Long Live Pakistan" when the soldiers from the Punjab Rangers paramilitary force and the army reached the scene to join the police reinforcements.

The terrorists shot at helicopters circling over the centre to identify their positions, without doing any damage. Several explosions were also heard from inside the compound.

A police official trapped inside the complex told the Aaj news channel that he and 12 other police were hiding in one room and they only had a single rifle to defend themselves.

"We cannot see them," Subinspector Mohammad Riaz told the news channel on a mobile phone. "When they face us, they hurl grenades or open fire. We have only one gun. May God destroy these culprits."

The attack came three weeks after at least 10 assailants ambushed a convoy carrying the Sri Lankan national cricket team to a stadium in Lahore, killing six police officers and two civilians and injuring eight members of the cricket team.

Both commando-style actions in Lahore are similar to those carried out in the Indian financial hub of Mumbai on November 3. More than 170 people died and more than 300 were injured there in the November massacre that lasted about two days.

The Pakistan-based militant outfit Lashkar-e-Taiba has been blamed for the Mumbai attacks.

Malik said the attackers Monday were operating in an organized and tactical manner. He blamed Taliban elements and Islamist militants for the siege.

"We had credible information that the TTP (Pakistani Taliban Movement) and al-Qaeda fighters held a meeting recently and decided to send militants across the country," he said. "They are out in large numbers, and we had fears of such attacks."

Malik told reporters that the militant organizations had proliferated over the years and authorities were struggling to map out their activities. (dpa)