At least 22 militants were killed today in clashes with government forces in Pakistan tribal lands bordering Afghanistan, dpa quoed a security official as saying. The fighting took place in Orakzai district, where troops backed by artillery and jet fighters launched an offensive last week against Taliban and al-Qaeda militants. "Ten terrorists" were killed when helicopter gunships pounded their hideouts after a tip off, said the official who spoke on condition of anonymity, as he was not authorized to talk to media. The forces also targeted two vehicles with fleeing militants. Six militants died in the attack and their vehicles were completely destroyed, the official said. Also on Thursday six militants were killed and a number of others injured when two rival Taliban groups sprayed each other with bullets following a dispute in Orakzai. Orkzai is the latest battleground, after militants moved there following an attack in South Waziristan by the military mid-October, which also displaced thousands of civilians. The country's army chief, Lieutenant General Ashfaq Parvez Kayani, in an open letter Thursday urged the displaced people to return to South Waziristan, in a bid to show the army's control over the area. The militants have lost some key strongholds in the army operations. Official figures show more than 200 militants have been killed.