Mullah Omar, the leader of the Taliban that OBL once called "the Caliph," has eluded the NATO & US forces since the beginning of the operation in Afghanistan. His whereabouts are suspected to be in Afghanistan, but Afghani Secret Services' recent captures of Taliban spokesmen has put that in doubt, continuing the spat between the countries of Pakistan and Afghanistan.

Al Jazeera reports that Nato-led troops and Afghan forces arrested Muhammad Hanif, a Taliban spokesman, in Nangarhar province in the east after he crossed through a border checkpoint from Pakistan.
Al Jazeera, 01/17/2005

On Monday, NATO caught a top spokesman for the Taliban and on Tuesday, another.

The captured militant, whom NATO did not identify, had fled another recent offensive by Afghan and NATO forces in the south of the country, the alliance said. He was captured in the Gereshk district of Helmand province late Tuesday
Sayed Ansari, the spokesman for Afghanistan's intelligence service, told reporters Wednesday that the Taliban spokesman's real name is Abdulhaq Haji Gulroz, a 26-year-old Afghan from Nangarhar's Chaparhar district.
Ansari said Hanif had lived in northwestern Pakistani city of Peshawar and had told investigators that the Taliban's reclusive leader Mullah Omar was living in the southwestern Pakistani city of Quetta, protected by that country's intelligence agency.
Afghan raid nets Taliban chief, 01/17/2007
"He lives in Quetta," Hanif says of Omar, as he sits in an oversized chair in a dimly lit room, as Afghan agents pepper him with questions. "He is protected by ISI," the 26-year old said in a quiet voice, referring to Pakistan's Inter-Services Intelligence agency.
Captured Taliban spokesman says militant leader lives in Pakistan, International Herald Tribune, 01/17/2007

This capture was confirmed by another Taliban spokesperson, Qari Yousef Ahmadi. This spokesperson, Ahmadi, contradicted a 12/13/2006 US report of having killed a top Taliban commander in Helmand province, Afganistan, Mullah Akhtar Mohammad Osmani. He did confirm the death of four Taliban commanders, including Mullah Abdul Zahir.

Quetta's the capital of Baluchistan province in Pakistan, a city of approx. 800k people and something like the 9th largest city.

A few days ago, on 01/05, Qatar's Gulf Times/Reuters published that Mullah Omar is in e-mail contact with the world and OBL and claims he's in Afghanistan.

So, who's to be believed? Pakistan's history of dissembling and mismanagement of their tribal areas vs. a Taliban PR guy who could very well be lying. Or, if he's not and there is protection from the Pakistani government, he's in no trouble revealing that fact, because no one in Pakistan'll scour Quetta.