Pakistani police have arrested a number of suspects in the case of a 14-year-old girl shot in the head by the Taliban after promoting girls' education and speaking out about the group's atrocities.

A senior police official in Mingora, Afzal Khan Afridi, declined to give any further details.

Ms Yousufzai and two other girls were shot on Tuesday in a school bus on their way home from school. The young activist is being treated at a hospital in Rawalpindi.

A spokesman said she was in "satisfactory" condition but the next few days will be critical. She is being kept unconscious and on a ventilator.

The bullet entered her head and went into her neck towards her spine, but it was too soon to say whether she had any significant head injury.

The shooting sparked outrage around the country and world and an outpouring of support for a girl who took on the Taliban.

The group's leadership decided two months ago to kill her - and then sent out a hit squad to carry out the job, a spokesman for the Taliban's Swat Valley chapter says.

He said she was warned three times to stop her activities promoting "Western thinking," but she did not.

He said the last warning was conveyed a week ago.

Two of the attackers had expertise in shooting people in the head. The hit squad carefully examined the girl's route from school to her home, he said.