Four policemen were killed when a suicide attacker disguised in uniform blew himself up inside a provincial police headquarters in eastern Afghanistan on Saturday, a spokesman said. Eleven other officers were wounded when the attacker detonated his explosives in the main police base in Sharan, the capital of Paktika province, which shares a border with Pakistan, provincial spokesman Mukhlis Afghan said. 'The suicide attack caused 15 casualties to the police force. Four of the 15 wounded died in hospital and the rest are receiving treatment,' he said. Taliban insurgents principally use suicide attacks and home-made bombs to attack government forces and more than 140,000 US-led troops fighting a counter- insurgency campaign mostly in the south and east of the country. Paktika province is deeply embroiled in the rebels' campaign to return to power as it lies across the border with Pakistan's tribal area of South Waziristan, believed to be the base for the Taliban-allied Haqqani network. A suicide attack by a Jordanian triple agent at the CIA base in neighbouring Khost province last December killed seven Americans and his Jordanian handler, marking the CIA's worst loss in a single day in more than 25 years. The police are seen as central to the goal of getting the Afghan authorities to take the lead in the fight against the Taliban, who were ousted after the US-led invasion in late 2001 but who continue to wage a deadly guerrilla war. There are currently about 80,000 police officers and US and NATO forces hope to bring that number up to 134,000 by October next year, alongside the 170,000 personnel planned for the army by the same date. US military leaders back the government's plan for the Afghan police and army to assume responsibility for security by 2014, with the timetable agreed at a landmark NATO summit in Lisbon this month. On the military side, 661 foreign service personnel have now lost their lives so far this year, according the independent icasualties.org website, which tracks coalition fatalities. The toll is the highest since the US-led invasion in late 2001. Last year 521 NATO soldiers died. The number of ordinary Afghans killed in the conflict rose by a third in the first six months of 2010 to 1,271, with most deaths caused by insurgent attacks, the UN said in August. 