Nearly 60 people have been killed in a series of attacks by US drones in the past 24 hours in Pakistan's Khyber tribal district. According to official’s report, at least 50 died in three unmanned air strikes in the Tirah Valley, a day after seven others was killed nearby. Security officials say all the dead in the attacks are militants – a claim that cannot be independently confirmed. US drone attacks in Pakistan's tribal region have increased under the presidency of Barack Obama, often occurring several times every week. But the US now appears to be expanding its campaign to other parts of the tribal belt, as most of these attacks have been in the Waziristan region. There have been more than 100 attacks by pilotless US aircraft in 2010, most of them in North Waziristan. Drone strikes are credited with killing some top insurgents, but are also blamed for civilian deaths. Pakistan's military has launched offensives in parts of the north-west, including the Swat Valley, but the insurgents continue to mount attacks.Meanwhile, the CIA has withdrawn its top spy from Pakistan, amid threats to his life.