ISLAMABAD: At least two security personnel, including a lieutenant colonel, were killed in a clash with militants in Shawal area of North Waziristan, military’s media wing said on Monday, adding that six militants were also killed in the clash.

The region is remote and off-limits to journalists, making it difficult to verify the number and identity of those killed.

The final phase of Zarb-i-Azb operation in North Waziristan got under way on Thursday as troops launched a ground offensive in Shawal Valley, one of the last strongholds of militants in the region.

“We have moved into the last stage of the operation. The ground action in Shawal has commenced,” military spokesman Maj Gen Asim Bajwa told Dawn.

The Zarb-i-Azb operation began in June last year and the army says it has cleared most of North Waziristan.

Shawal Valley and a pocket to its northwest are the remaining areas that need to be cleared.

The terrorists, except for those who have fled to Afghanistan, are said to be holed up in Shawal. One of the reasons the fleeing militants chose Shawal as their refuge was a perception that Shawal was inaccessible.

“The militants have been besieged there for weeks now,” the ISPR chief said.

The area is considered to be a stronghold of Gul Bahadur, a warlord once considered to be pro-government, and an Al Qaeda sanctuary. Presence of Haqqani network militants was also reported from the valley when a US drone strike on June 6 killed nine Haqqanimen there. Shawal has been the focus of US drone attacks this year.

Shawal Valley, which borders South Waziristan on one side and Afghanistan on the other, has the toughest terrain in the tribal agency, with treacherous mountains as well as forests.

It is said that the Shawal offensive could be the toughest part of the campaign.

"We are expecting opposition and are fully prepared for it," Gen Bajwa said.