Three people including two paramilitary soldiers were killed in a roadside bomb blast in northwest Pakistan's tribal district of Orakzai, says officials.

An improvised explosive device planted by militants went off in the town of Ibrahimzai during a routine patrol by paramilitary soldiers, a security official said on Saturday.

"Two soldiers and one civilian were killed in the blast," Abdul Qadir, a local administration official, told AFP.

Seven other people -- one soldier and six civilians -- were wounded in the explosion near the bazaar in Ibrahimzai, he said.

A military official in the provincial capital Peshawar confirmed the incident, saying the wounded had been taken to the local hospital.

Orakzai is one of the most lawless areas in Pakistan's northwest tribal region, which is made up of seven rugged districts near the Afghan border.

Washington has branded the semi-autonomous tribal belt as the epicentre of Al-Qaeda and its Taliban allies fighting in Afghanistan.

Pakistan launched a major operation in Orakzai in March last year after militants fled a sweeping offensive in the nearby tribal district of South Waziristan.

Late last year military officials said lower Orakzai had been cleared, but the militant threat persisted in some pockets of the upper part of the area.

Around 4, 000 people have been killed in militant attacks in Pakistan since July 2007.