At least 21 suspected militants have been killed in two separate attacks of an unmanned US drone aircraft in north-west Pakistan, according to Pakistani security officials.

The missiles struck targets in the North Waziristan tribal region near the Afghan border.

Pakistan has previously complained that such attacks violate its sovereignty.

Last month, President Barack Obama defended the use of drones to target militants in Pakistan’s tribal areas.

Security officials said that in the first attack two missiles killed at least five militants. Several others were wounded, although the exact number could not be established.

A second attack in the same area, near Miranshah, the main town of North Waziristan, killed 15 Uzbek fighters, officials said.

There is no way of getting independent confirmation of the figures as reporters are prevented by the authorities from travelling to the region.

The area is known as a sanctuary in Pakistan for the Taliban and al-Qaeda-linked militants.

Another drone attack last week hit a house in Spalga, killing at least nine people, including some Pakistani Taliban militants.

The US does not normally comment on drone operations, which have killed hundreds of people in recent years.

The recent attacks come a week after officials said one of the most senior al-Qaeda militants in Pakistan, Badar Mansoor, was killed in a US drone strike.

Islamabad is hosting talks on Thursday and Friday with leaders of Afghanistan and Iran to discuss counter-terrorism co-operation, and strengthening regional stability.