PESHAWAR/MIRANSHAH, Pakistan: At least nine Pakistani servicemen were killed on Sunday when a roadside bomb hit an army convoy passing through the troubled region of North Waziristan near Pakistan’s border with Afghanistan, security sources said.

Militant groups including the Taleban and Al-Qaeda operate in the volatile tribal region, often launching attacks on troops and civilians from mountain hideouts on the porous border.

Initially, army sources said three soldiers had been killed but later a security official in the regional town of Miranshah raised the death toll to nine. At least 21 soldiers were wounded.

US drone strikes often target insurgents in lawless and inaccessible North Waziristan, home to both homegrown and foreign militants.

The incident happened in the Boya area of North Waziristan, a stronghold of militants linked to the Taleban and Al-Qaeda.

The incident occurred due to an explosion caused by an improvised explosive device, according to a senior security official.

He said the bomb hit a convoy of of vehicles carrying regular soldiers and members of the paramilitary Frontier Corps to the town of Miranshah from the Datta Khel area.

Another security official confirmed the toll.

Pakistan is battling a Taleban-led domestic insurgency that has killed thousands of civilians and security personnel since 2007.

Troops have been fighting for years against homegrown insurgents in the tribal belt, which Washington also considers the main hub of Taliban and Al-Qaeda militants plotting attacks on the West and in Afghanistan.

North Waziristan is frequently targeted by US drones. A drone strike on Saturday on a compound in the Heso Khel area killed at least four militants.