The operation on Malala Yousafzai, a campaigner for girls' rights, went well, her father told the BBC.

The attack sparked outrage among many Pakistanis, who gathered in several cities for anti-Taliban protests and held prayers for the girl's recovery.

The militants said they targeted her because she "promoted secularism".

A spokesman for the Islamist militant group, Ehsanullah Ehsan, told BBC Urdu on Tuesday she would not be spared if she survived.

The BBC's Aleem Maqbool in Islamabad says the authorities will now have to consider how to protect the girl.

He says her family never thought about getting security because they just did not think that militants would stoop so low as to target her.

Two other girls were injured in Tuesday's attack, one of whom remained in a critical condition on Wednesday.

Malala Yousafzai came to public attention in 2009 by writing a diary for BBC Urdu about life under Taliban militants who had taken control of the valley. The group captured the Swat Valley in late 2007 and remained in de facto control until they were driven out by Pakistani military forces during an offensive in 2009.

While in power they closed girls' schools, promulgated Islamic law and introduced measures such as banning the playing of music in cars.

Thousands of people around the world have sent the teenage campaigner messages of support via social media.

Schools in the Swat Valley closed on Wednesday in protest at the attack, and schoolchildren in other parts of the country prayed for the girl's recovery

Late on Tuesday, she was flown from Mingora, where the attack happened, to the city of Peshawar, 150km (95 miles) away, for surgery.

Doctors in Peshawar operated on her for hours before managing to remove the bullet early on Wednesday. "The operation went well, now she is ok and the swelling is down," her father, Ziaudin Yousafzai, told BBC Pashto.

"Please pray for her, the next 24 to 48 hours are very important. Doctors are saying we don't need to shift her. It's good for her to be here now."