Islamabad - A suspected US drone attack has killed four militants in north-western Pakistan, local intelligence officials said.

The drone fired a missile, destroying a house in a market in Miranshah town in North Waziristan tribal district.

North and South Waziristan are regularly targeted by drone missiles.

The US says the region provides sanctuary to al-Qaeda and Taliban insurgents who are involved in attacks on Nato forces in Afghanistan.

Last week, a US drone attack killed at least 21 militants in North Waziristan. Among the dead were several foreigners believed to be part of the Haqqani network.

Last month, drone strikes killed at least 30 people in less than 24 hours in the area.

Drone attacks have escalated in the region since President Barack Obama took office in 2008. More than 100 raids were reported in the area last year.

The US does not routinely confirm drone operations, but analysts say only American forces have the capacity to deploy such aircraft in the region.

Pakistan publicly criticises drone attacks, saying they fuel support for militants. But observers say the authorities privately condone the strikes, although there have been recent signs that they want to limit the scope of such attacks.

A number of militants, some of them senior, have been killed in the raids, but many civilians have also died.