Some private Afghan television channels reported Monday that Omar was killed en route from Quetta to North Waziristan but the Taliban strongly denied the reports.
Lutfullah Mashal, a spokesman for Afghanistan's intelligence bureau, told reporters he "cannot confirm officially whether [Omar] is dead or alive," The Washington Post reported.
He said Omar has been living in Quetta, capital of Pakistan's Baluchistan province, for about a decade and quoted unidentified sources on the Pakistani side of the border as saying the Taliban leader had "disappeared from his location in the last four or five days," the report said.
"Our sources and senior Taliban commanders have confirmed that they have not been able to contact Mullah Omar," Mashal said. "So far, we cannot confirm the death or killing of Mullah Omar officially, but we can confirm that he has ... disappeared from his hideout in Quetta of Baluchistan."
A Taliban statement said: "Claims and rumors were spread ... by the Kabul stooge regime's intelligence directorate, other officials and some media outlets that the esteemed Amir ul-Mumineen [Omar] was martyred in Pakistan. We strongly reject these false claims of the enemy," the Post reported.
Omar was close to Osama bin Laden, the al-Qaida leader who was killed May 2 by U.S. forces in a raid on his compound in Pakistan's garrison town of Abbottabad, northeast of Islamabad.