Militants loyal to Baitullah Mehsud, the Pakistani Taleban leader believed to have been killed in a US missile attack, have killed 17 fighters from a rival faction in an ambush, Taleban and intelligence officials said Sunday. The Mehsud clansmen ambushed vehicles carrying men from Maulvi Nazir Wazir's group in South Waziristan, a tribal region on the border with Afghanistan, late Saturday night. “They were hiding behind the rocks and, as soon as our people reached there, they opened fire. It was so sudden and quick that none of our men fired back,” Shaheen Wazir, Maulvi Nazir's spokesman, told Reuters by telephone. An intelligence officer in the region said the attackers also fired rocket-propelled grenades at the pick-up trucks carrying the Wazir fighters towards Wana, the main town in South Waziristan. A resident saw militants carrying some of the dead bodies into Wana. – ReutersThe Mehsud and Wazir tribes are the two dominant clans in a region long seen as a safe haven for the Taleban and Al-Qaeda. While Baitullah Mehsud's main focus was on fighting the Pakistani government and security forces, Maulvi Nazir's group has been heavily involved in the insurgency over the border in Afghanistan. The attack on Maulvi Nazir's fighters is more significant than earlier clashes between Mehsud's fighters and men led by two other militant commanders, Turkistan Bitani and Misbahuddin Mehsud. In March, Baitullah Mehsud had forged an alliance with Maulvi Nazir and a commander in North Waziristan, Hafiz Gul Bahadur.