DERA ISMAIL KHAN - At least three security personnel were killed after a raid on a Pakistan Army checkpoint in South Waziristan, security officials say, as the military presses on with an offensive in the Shawal Valley.

Pakistan began a ground offensive in the deeply forested ravines of the valley, a historical smuggling route which straddles the border between North and South Waziristan, on Friday.

According to reports, terrorists attacked a security check post in Ladha and opened fire, resulting in the demise of three security personnel: Jafar Hussain, Mohammad Ali and Arsalan Khan. The assailants escaped after the attack.

Ladha, once a stronghold of the Taliban, lies between Kaniguram and Makeen. It is the largest of the agency’s administrative sub-divisions in terms of population. The army had regained control of Ladha from the Taliban in 2009 during Operation Rah-i-Nijat. The region is mountainous and has several Taliban sanctuaries.

“Militants attacked with heavy weapons, including (Rocket Propelled Grenades) and machine guns. Forces replied to the attack we are checking for the militants’ casualties,” a security official told Reuters on condition of anonymity.

On Monday, two security forces personnel, including a lieutenant colonel, were killed in an exchange of fire with militants in the Shawal valley, Pakistan’s military said in a statement. At least six militants were also killed in that exchange, the military said.

Both attacks were claimed by a faction of the Tehreek-e-Taliban Pakistan (TTP), who the army has been battling in North Waziristan since it launched a full-scale military operation in the area in June last year.

“We will not let the army enter Shawal under any conditions,” Azam Tariq, a Taliban spokesperson, told Reuters on Tuesday, adding that dozens of Taliban fighters had been involved in the raids.

The Shawal offensive marks the latest phase of a military operation in Waziristan, which the army says has resulted in the deaths of more than 2,700 militants and the clearance of most of North Waziristan, a historical hotbed of militancy.

On Tuesday, the military said it had destroyed a militant training camp and ammunition dump in gunship helicopter strikes in the Gurbaz area of Shawal. The statement added that a number of suspected terrorists were also killed in air strikes.

The details could not be independently verified as access for media personnel is severely restricted in the region.

The Pakistani Taliban has been battling the Pakistani state since the group's formation in South Waziristan in 2007, and has the ultimate goal of enforcing a strict interpretation of Islamic sharia law on the country.