Mullah Abdul Ghani Baradar, who ranks below only Taliban founder Mullah Mohammad Omar, was held in the southern Pakistani port of Karachi.
A Pakistani officer said he 'was talking' to interrogators.
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Pakistan's spy agency has been accused in the past of protecting top Afghan Taliban leaders sheltering in the country, frustrating Washington. 
Caught out: Bardar was captured in the southern Pakistan city of Karachi. It has a large population of Afghan Pashtuns. Pakistan supported the Afghan Taliban before 9/11
Moving against Baradar , a close associate of Osama Bin Laden, could signal that Islamabad increasingly views the Afghan Taliban, or at least some of its members, as enemies.
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The arrest ten days ago came amid a new push by the U.S. and its Nato allies to negotiate with some Taliban leaders as a way to end the eight-year Afghan war. 
The reported capture of Taliban commander Mullah Abdul Ghani Baradar comes as Nato forces take part in the biggest offensive against the Taliban since hostilities began in Afghanistan
Karachi, Pakistan's largest city, has been increasingly considered a likely hiding place for Taliban commanders, even though it is far from the border.
It has a large population of Pashtuns, the ethnic group that makes up the Taliban.
Baradar was promoted to head the Taliban's military council after the death of commander Mullah Akhtar Mohammed Usmani in 2006.
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Mullah Baradar was arrested in Karachi in a joint U.S. and Pakistan operation
His area of direct responsibility stretches over Kandahar, Helmand, Nimroz, Zabul and Uruzgan provinces.
Baradar was deputy defence minister in the Taliban regime that ruled Afghanistan until 2001.
Last night a Taliban spokesman insisted that he was still free, branding the capture reports as propaganda aimed at undermining Taliban resistance to the current coalition offensive.
