A U.S. newspaper on Monday reported that a top Taliban commander had been caught in a secret U.S.-Pakistan joint operation in Karachi.

The report released on the New York Times website identified the Taliban commander as Mullah Abdul Ghani Baradar, and the capture was described as "the most significant Taliban figure to be detained since the American-led war in Afghanistan started more than eight years ago."

Citing government officials, the report said that the operation had been carried out by personnel from Pakistan's military spy agency - Inter-Services Intelligence and the U.S. Central Intelligence Agency.

But details of the raid remained unclear.

Baradar has been in custody in Pakistan for several days and under investigation by the U.S. and Pakistani intelligence officials, who are hoping he can provide insight into the Afghan-grown militant group and intelligence leading to the whereabouts of Mullah Muhammed Omar, it said.

The New York Times released the report several days after it acknowledged the news story on Thursday. This was done at the request of the White House because there were concerns that the disclosure would negatively affect the intelligence-gathering efforts, it added.

The U.S.-launched war in Afghanistan suffered setbacks last year as the Taliban's insurgence regained its momentum and stepped up attacks.

Since President Barack Obama took office, efforts have been made to shift the focus of the war from Iraq to Afghanistan to win back the upper hand over the Taliban. This includes a new strategy on Afghanistan and Pakistan, the decision to send 30,000 additional troops, and the U.S. call on its allies in Europe to commit more resources to the war.

However, the Obama administration has been under pressure, having been criticized for the increasing war budget and troop casualties.

The U.S.-Pakistan cooperation on counter-insurgency was also questioned since some "American intelligence officials believed that Pakistan's security services have covertly supported the Taliban with money and logistical help," the report said.

The capture of Baradar, however, shows "a new level of cooperation from Pakistan's leaders," who have been gradually convinced they could no longer support the Taliban in Afghanistan, it added.

According to the report, Baradar was born in 1968 in a village in Afghanistan's Oruzgan Province. He was a skilful military leader who ran many high-level meetings of the Taliban's top commanders in Afghanistan.

He is the No. 2 in the Afghan-grown militant group, second to its founder and spiritual leader, Mullah Omar.

After the Sept. 11 terrorist attacks, Baradar was assigned to take charge of the overall Taliban forces in northern Afghanistan and was captured by the Afghan military in November 2001. However, he was released afterwards due to "Pakistani intelligence operatives' intervention."