KABUL, Afghanistan - If the latest reports of Mullah Mohammed Omar's demise are greatly exaggerated - as Mark Twain once quipped about his own premature obituary - they nonetheless offer a glimpse of the zeitgeist in Afghanistan and Pakistan after the death of Osama bin Laden.

A Taliban spokesman Monday vehemently denied assertions that the movement's spiritual leader had died or been killed, even as Afghanistan's main intelligence service said the reclusive cleric had disappeared from his alleged Pakistan hideout.

The Taliban spokesman, Zabiullah Mujahid, said by phone that the one-eyed, self-declared "leader of the faithful" - long thought to be hiding in Pakistan - was well, directing the group's military campaign in Afghanistan. Western diplomats in Kabul, and tribal and intelligence sources in Pakistan, expressed skepticism over the death rumors, which have surfaced many times.

But the wildfire-like spread of Monday's reports, aided by social media, reflected the intense speculation surrounding Omar's fate, which has heightened since Navy SEALs killed bin Laden in a raid in Pakistan. They also spotlighted an increasingly combative and complicated relationship between Afghanistan and its neighbor Pakistan over the sheltering of extremists.

The death rumors about Omar appeared to emanate mainly from Afghanistan's main intelligence service, the National Directorate for Security. Its spokesman, Lutfullah Mashal, said in Kabul that Omar disappeared several days ago from Pakistan's Baluchistan province, seat of the Taliban leadership council known as the Quetta shura.

"Our sources and senior Taliban commanders have confirmed that they have not been able to contact Mullah Omar," Mashal said at a news conference. "So far, we cannot confirm the death or killing of Mullah Omar."

Earlier, Mashal told the Associated Press that Omar was thought to have been transported from his base in Quetta to the tribal agency of North Waziristan with the knowledge of Hamid Gul, a former Pakistani intelligence chief known to be sympathetic to the insurgents. Gul went on Pakistani television to deny the report, adding that he did not even know Omar.

Omar has long had near-mythical status in the tribal borderlands. Nearly a decade ago, in the wake of the Sept. 11 attacks, he defied Western demands to hand over bin Laden.

Omar's resistance triggered the U.S.-led invasion of Afghanistan in 2001, and both he and bin Laden became the subject of international manhunts, with multimillion-dollar bounties on their heads.

A Pakistani intelligence official who asked not to be named said the country's intelligence community had no information to suggest Omar was dead.

Siege at Pakistani Base Raises New Fears

The ability of only six armed extremists to storm a Pakistani navy base in the city of Karachi and hold out for 16 hours raised new fears Monday about the security of Pakistan's military installations, including its nuclear- weapons sites.

The attack, late Sunday into Monday afternoon,

left 10 Pakistani security personnel dead. At least two U.S.-supplied planes were destroyed. Six Americans who were providing training at the site were rescued by Pakistani security forces during the shoot-out.

It was an ignominious attack for Pakistan's armed forces, coming three weeks after U.S. helicopters flew deep into Pakistan undetected in a raid that resulted in Osama bin Laden's killing.

Interior Minister Rehman Malik said the Karachi attackers had used a blind spot between security cameras to enter the base unnoticed, suggesting someone on the base helped plan the attack.

A Pakistani Taliban spokesman said the attack aimed to avenge bin Laden's killing.

- McClatchy Newspapers