Malala Yousafzai was shot in the head on her way home from school in Mingora, the main town in the Swat Valley.
The president and prime minister have led condemnation of the attack.
Initial reports suggested she was out of danger, but there is growing concern over her condition with some reports saying she may need treatment abroad.
A Pakistani Taliban spokesman told the BBC they carried out the attack.
Ehsanullah Ehsan told BBC Urdu that they attacked her because she was anti-Taliban and secular, adding that she would not be spared.