A suicide attack targeting police killed at least 16 people, including five policemen, in Pakistan's northwestern tribal belt along the Afghan border on Friday, officials said.
The target of the attack was tribal police in Khar, the main town of Bajaur tribal district, where Taliban linked to Al-Qaeda are active, officials told AFP.
"The death toll has risen to 16. Five of them were tribal policemen," Abdul Haseeb, an administration official in Khar, told AFP.
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Tariq Khan, a senior government official in Khar, said the bomber was on foot and detonated his explosive vest when he reached a police checkpost.
There was no immediate claim of responsibility. The attack came two days after Pakistan went on a high state of alert for the first anniversary of Osama bin Laden's killing by American troops, fearing a wave of revenge attacks.
Tribal police, who are recruited to help the government fight Taliban militants in the tribal belt, are frequently attacked.
Two bomb attacks killed at least five people -- pro-government tribal elders and security personnel -- in same district on Thursday.
Bajaur has been one of the hardest-hit zones in Pakistan's battle to contain a local Taliban insurgency in the northwest.
The military conducted major anti-Taliban offensives in Bajaur in August 2008 and February 2009, and has repeatedly declared the district secure.
But militants have still proved able to strike.
Pakistan has battled homegrown insurgents in the tribal belt for years. More than 3,000 soldiers have died but Pakistan has resisted US pressure to do more to eliminate havens used by insurgents fighting the Americans in Afghanistan.
The United States conducts a secretive drone war against Taliban and Al-Qaeda militants based on Pakistani soil, despite increasingly vocal public denunciations from the government that initially gave its tacit approval to the strikes.
Relations between Pakistan and the United States have lapsed into stalemate since the covert American raid that killed bin Laden last May and US air strikes that inadvertently killed 24 Pakistani soldiers last November.
Pakistan has shut down NATO supply lines into Afghanistan and last month parliament approved new guidelines on relations with the United States, which included a call for an end to drone strikes in Pakistani territory.
They also include a ban on transporting weapons through Pakistan to Afghanistan and a call for an unconditional apology for the November air strikes.
It remains unclear whether the impasse with the Americans -- which Islamabad blames on Washington's reluctance to apologise -- can be solved before this month's NATO summit on Afghanistan in Chicago, to which Islamabad has been invited.
