A teenage suicide bomber targeted police in a bustling Pakistan town square on Friday, killing at least 24 people and wounding dozens in the tribal area near the Afghan border, officials said.
The Taliban claimed responsibility, saying it had wanted to kill the local chief and deputy of a tribal police force recruited by the government to help defeat the Islamist insurgency in the northwest.
Both died in the attack in Khar, the main town of Bajaur district, after a bomber who intelligence officials said was aged 14 to 16 detonated explosives strapped to his chest.
Bajaur has been one of the toughest battlegrounds in Pakistan's fight against a northwestern Taliban insurgency. The military conducted major offensives there in 2008 and 2009 and has repeatedly declared it secure.
Friday's blast was the deadliest bombing in Pakistan since February 17, when 31 people were killed by a suicide attack on Shiite Muslims in the tribal district of Kurram.
"The death toll has risen to 24," Islam Zeb, the administrative head of Bajaur tribal district, told AFP. He had earlier said 20 people were killed.
Raids were later carried out in the surrounding areas of Khar and two men aged 17 and 18 were arrested and suicide jackets found, he said.
At least five policemen, including the local tribal police chief and his deputy, were among the dead and 46 people were wounded. Shops and a restaurant were destroyed.
Ehsanullah Ehsan, spokesman for the Pakistani Taliban, claimed responsibility, saying that anyone involved in "activity" against the Taliban "will be treated with iron hands".
"Our attacks will continue until (US) drone strikes end," Ehsan told AFP.
It was the third bomb attack in two days in Bajaur, after twin blasts killed five people -- including pro-government elders and security personnel -- on Thursday.
The violence highlights the insurgency in Pakistan at a time when Islamabad is under renewed US pressure crack down on militants based on its soil, such as the Haqqani network, blamed for a spectacular assault on Kabul last month.
According to an AFP tally, around 5,000 people have been killed in attacks blamed on the Taliban and its allies since July 2007, when Pakistani troops raided an extremist mosque in Islamabad, sparking a bloody insurgency.
Documents released by the US Thursday showed that Osama bin Laden had been unhappy with the Pakistani Taliban for killing civilians and that Al-Qaeda leaders wrote to its chief, Hakimullah Mehsud, urging him to mend his ways.
Pakistan has also lost more than 3,000 soldiers in the fight against homegrown insurgents but has resisted US pressure to do more to eliminate havens used by those fighting the Americans in Afghanistan.
The United States conducts a secretive drone war against Taliban and Al-Qaeda militants on Pakistani soil, despite increasingly vocal public denunciations from the government, which 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 in 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.
It remains unclear whether the impasse with Washington can be solved before this month's NATO summit on Afghanistan in Chicago, to which Islamabad has been invited.