PESHAWAR: As many as six terrorists were killed by security forces in North Waziristan Agency’s Shawal Valley during a ground offensive on Monday.Lieutenant Colonel Faisal Malik and a soldier also embraced martyrdom.According to a statement issued by the Inter-Services Public Relations (ISPR), the terrorists were killed in an exchange of fire with the soldiers.The final phase of Operation Zarb-e-Azb 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 Major General Asim Bajwa told a private TV channel.The operation began in June 2014 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 terrorists 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.Shawal Valley, which borders South Waziristan on one side and Afghanistan on the other, has the toughest terrain in the tribal agency.