A top Taliban military commander has been captured by US and Pakistani intelligence forces, US media is reporting.

However, the Taliban has denied his arrest and said he was still leading the fight in Afghanistan.

Mullah Abdul Ghani Baradar was said to have been arrested in Karachi 'several days ago', the New York Times and US media said, citing unnamed US government officials.

If confirmed, the arrest would be a huge blow for the Taliban.

The report emerged as 15,000 US, NATO and Afghan troops press on with a major assault to capture the Taliban bastion of Marjah in southern Afghanistan.

The operation is key to Washington's new strategy for turning around the costly war.

The New York Times billed the Afghan-born commander as top lieutenant to Taliban leader Mullah Mohammad Omar, and said he was currently being interrogated by Pakistani and US officials.

Denying the capture, the Taliban accused US officials of trying to deflect attention from 'serious resistance' put up by Taliban fighters in Marjah.

'He is currently in Afghanistan, where he is leading all jihadi activities...

'The sole goal of such baseless reporting and propaganda is to make up for the failure in Marjah,' Taliban spokesman Yousuf Ahmadi told AFP by telephone from an undisclosed location.

Officials from Pakistan's military and the government were not immediately available for comment on the reports.

Senior police officials in Karachi said they had no information.

Mullah Abdul Ghani Baradar is in charge of the Taliban's military operations and leadership council.

He was a close associate of al-Qaeda leader Osama bin Laden before the 11 September, 2001 attacks on the US, the New York Times said.

It quoted US officials saying they hoped his capture will lead them to other senior Taliban officials.