Even by the standards of a bullet- and bomb-dodging Taliban commander, Hakimullah Mehsud has displayed notable survival skills. The Pakistani Taliban chief was believed dead in a leadership duel last summer, only to stage a news conference a few days later. A U.S. drone strike in January was followed by intense speculation about his fate, then statements by Pakistani intelligence officials that he was '100 percent' dead. On Thursday, those intelligence officials circulated another message: Mehsud is alive. Earlier reports of Mehsud's death _ repeated by U.S. officials _ were hailed as a potentially fatal blow to the Pakistani Taliban, a loose network of border- based militants that has carried out a cascade of suicide attacks in recent years. News of his survival again underscored the staying power of a group that Pakistan's military has targeted with unprecedented force in the past year. It also exposed blind spots for the Pakistani and U.S. intelligence services, which struggle to develop reliable information in areas where the Taliban has reigned. Offensives in the tribal areas over the past six months have scattered fighters and prompted some Pakistani officials to deem the group hobbled, but its leadership remained at large and attacks claimed by the Taliban never fully ceased. In the Swat Valley, where the army pushed out militants last spring, a recent string of targeted killings has sparked fears of a Taliban resurgence. But Mehsud is not necessarily back. He may have survived the January attack, but he was wounded, and has been sidelined ever since, three senior intelligence officers said. He has been replaced by Wali ur-Rehman, a South Waziristan commander who was Mehsud's adversary in the leadership duel last August, they said. The twists in Mehsud's reported fate reflect significant human intelligence gaps in Pakistan's craggy tribal areas, officials and analysts said. More than 70 Pakistani agents and informants have been killed in the region since 2004, intelligence officials said, and there are regular reports of suspected spies whose throats are slit by militants. 'There was nobody to confirm it on the ground, actually,' an intelligence official said of Mehsud's fate after the drone strike. 'In these types of attacks ... people come and take out bodies, which is what they play upon _ they say innocent bystanders have been killed.' The drone that slammed into South Waziristan on Jan. 14 was part of a stepped-up campaign of drone attacks carried out by the CIA under the Obama administration. One Pakistani intelligence officer said a video showed that a building where Mehsud was staying had been so obliterated by the strike that analysts believed there could be no survivors. Though no body was found and Taliban fighters insisted Mehsud was alive, officials concluded Mehsud was dead when he did not publicly surface. Electronic and human intelligence gathered since, including intercepted phone calls, indicates otherwise, intelligence officials said. Mehsud's survival was first reported by the British newspaper the Guardian. After the January strike, a White House official called it '95 percent' certain that Mehsud had been killed. U.S. intelligence officials, for their part, continued to express uncertainty, and on Thursday, a U.S. counterterrorism official said there was still no hard evidence either way. But he said it was strange that Mehsud had not emerged to resolve the mystery. 'If Hakimullah really is alive, let him prove it,' said the official, who insisted on anonymity when discussing counterterrorism operations inside Pakistan. 'His group isn't one that traditionally led from the cave, in silence. His absence is the Taliban's problem, not ours. It's already been shown that he can be hit.' U.S. intelligence officials can often make precise assessments of casualties by closely monitoring the targeted buildings after the missiles have hit. But the CIA's drone-mounted cameras cannot always determine the identity of victims or how seriously they are injured. In a telephone interview Thursday, a Taliban fighter in North Waziristan, where Taliban leaders are believed to have taken refuge, said Mehsud had temporarily gone 'underground' but was unhurt and remained the leader _ and would soon produce a video to prove it. The Pakistani intelligence official said he did not know how seriously Mehsud was wounded but said he had been demoted, demonstrating the Taliban's 'fractured' nature. Intelligence officials say Taliban leaders, including Rehman and Mehsud, have been pushed from South Waziristan but remain in the tribal areas. Taliban attacks in Pakistan have dropped off in recent months. The Pakistani official said that trend is a positive sign, but he voiced caution, noting that as many as 8,000 Taliban fighters remain in the tribal areas. 'It could be they are just waiting and gathering troops,' the official said. 'This thing will continue, for sure.' _ Khan is a special correspondent. Staff writer Joby Warrick in Washington and special correspondent Shaiq Hussain in Islamabad contributed to this report. 