|Continuous attacks have prompted the US to urge Pakistan to do more to combat Islamist fighters [EPA]
The US military has said it has begun pulling some its troops out of Pakistan after the government requested a smaller presence, amid tensions over a US raid that killed Osama bin Laden.
Islamabad had asked for a scaling back of the US contingent of more than 200 troops earlier this month, Pentagon spokesman Dave Lapan said on Wednesday.
"We were recently notified in writing that the government of Pakistan wished for the US to reduce its footprint in Pakistan," he said. "Accordingly, we have begun those reductions."
He did not say how many troops would be pulled out. Most of the US personnel are special forces that train and advise Pakistani troops as part of efforts to counter al-Qaeda and other Islamist fighters.
The withdrawal of some US troops underscored the crisis between the two countries in the aftermath of the US raid that killed bin Laden on May 2, despite US diplomatic efforts to smooth over tensions.
The difficult relationship between Pakistan and the United States has come under severe strain since US commandos raided bin Laden's compound in the Pakistani city of Abbottabad, home to a military academy.
Days after the raid, General Ashfaq Kayani, Pakistan's army chief, said that any similar raid on Pakistani soil would prompt a review of military cooperation with the United States and informed army commanders of a decision to reduce the strength of US military personnel to "the minimum level".
American politicians have also demanded a re-evaluation of relations in the wake of the bin Laden raid, accusing Pakistan of playing a double-game of supporting Islamist fighters while enjoying a steady stream of aid from the US.
May 13 - 98 killed in Charsadda suicide bomb attack
May 16 - Gunmen shoot dead a Saudi diplomat in Karachi
May 18 - 17 including 15 insurgents killed in security post gun battle on the outskirts of Peshawar
May 20 - One Pakistani killed and 12 others, including two US nationals, wounded in US consulate attack in Peshawar
May 21 - Bomb attack kills 16 in Khyber tribal region
May 22 - Militants storm a naval base in Karachi, killing 10 military personnel and destroying two US-supplied surveillance aircrafts.
May 25 - At least six dead as car bomb explosion damages police station in Peshawar
Yousuf Raza Gilani, the prime minister, meanwhile convened a meeting of defence and military chiefs on Wednesday to review security measures, following a string of attacks by the Pakistani Taliban on security forces.
In the latest incident, nine security personnel were killed and a police station flattened in a suicide truck bomb in Peshawar on Wednesday.
Gilani admitted that "serious concerns were being expressed about Pakistan's ability to deal with the gravity of problems posed due to terrorism".
But a statement issued after the meeting failed to list any specific policies. "Security, defence and law enforcement agencies will be authorised to use all means necessary to eliminate terrorists and fighters," it said.
Last week, six fighters stormed a naval air base in Karachi, killing at least 10 people and destroying two US-made aircraft each costing $36 million in an attack that took around 17 hours, and hundreds of troops, to quell.
The United States has long put pressure on Pakistan to lead a major air and ground offensive in North Waziristan, a Taliban and al-Qaeda base used to launch attacks across the border in Afghanistan.
Pakistan has always maintained that any such operation would be of its own time and choosing, arguing that its 140,000 troops committed to the northwest are too overstretched in battles against fighters who pose a domestic threat.