The missiles hit a middle school at Sultana village in south Waziristan at 10 am, they said. Witnesses said tribesmen rushed to the site of the attack and pulled bodies out of the rubble. The school building was destroyed in the attack, they said.

This was the second US missile strike in the region since Thursday. Five militants were killed when a US drone yesterday fired three missiles at a vehicle near Wana, the main town of south Waziristan.

US drone aircraft regularly launch missile strikes against targets in north and south Waziristan. There has been a sharp increase in such operations against suspected Taliban and al-Qaida militants since August last year.

The two latest strikes hit an area controlled by Pakistani Taliban chief Baitullah Mehsud.

Pakistani officials say the US carried out around 50 missile strikes last year, killing hundreds of people, a majority of them civilians.

Foreign Minister Shah Mahmood Qureshi on Thursday asked the US to stop the missile strikes as they are counter-productive. Pakistan has also described such attacks as a violation of its sovereignty.