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Pakistani military officials say gunmen attacked the army's headquarters in Rawalpindi Saturday near the capital, killing six troops. Security forces have killed four of the attackers. Four others have taken up to 15 people hostage. No group has yet claimed responsibility for the attack.
The Pakistani military initially said it had the situation under control about an hour after gunmen, disguised in military uniforms, attacked a checkpoint at midday outside the heavily guarded headquarters.
But then military officials said some of the attackers had escaped into a security office building and were holding troops hostage.
Pakistani army spokesman, Major General Athar Abbas, said security forces are working to free the hostages. "The building is surrounded by the security forces and whatever happens and whatever the details of the operation (are), (they) will only be shared after the operation is conducted," he said.
Authorities have continued to block roads in the area.
Earlier in the day, at least three helicopters circled overhead as ambulances rushed to the scene. Occasional gunfire rang out in the area.
On Monday, a suicide bomber disguised in a paramilitary uniform attacked a U.N. office in nearby Islamabad, and on Friday, a suspected suicide car-bomber killed some 50 people in Peshawar.
The Pakistani Taliban claimed responsibility for the U.N. bombing and threatened to target other international organizations and Pakistani government and military locations.
In response to the attacks, Pakistani leaders have vowed to start a new offensive against militants in the country's tribal regions along the Afghan border.