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, officials say.

At least 50 died in three unmanned air strikes in the Tirah Valley, a day after seven others were killed nearby.

Security officials say all the dead in the attacks are militants - a claim that cannot be independently confirmed.

Meanwhile, the CIA has withdrawn its top spy from Pakistan, amid threats to his life, US intelligence confirms.

The Islamabad station chief had been identified in a lawsuit linking him to drone strikes, and media coverage of the legal action led to his name appearing on placards during anti-US protests in the Pakistani capital.