A senior commander of the Taliban-allied Haqqani network in Afghanistan who is also the uncle of its leader has been captured, the NATO-led International Security Assistance Force said on Saturday.

The announcement of Haji Mali Khan's capture comes as the US steps up pressure on Pakistan to act against the Haqqanis, linked to al-Qaeda and blamed for a string of attacks on Western targets.

The group's leadership is based in Pakistan's border regions and last week, the retiring chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, charged it was a "veritable arm" of Pakistan's intelligence service.

"Security forces detained Haji Mali Khan, uncle of Siraj and Badruddin Haqqani and the senior Haqqani commander in Afghanistan," ISAF said in a statement.

Khan was captured close to Afghanistan's porous border with Pakistan in Paktiya province Tuesday, it added, hailing the detention as "a significant milestone" in disrupting Haqqani operations.

"He reportedly worked directly under Siraj Haqqani, and managed bases and had oversight of operations in both Afghanistan and Pakistan," ISAF said.

"Mali Khan moved forces from Pakistan to Afghanistan to conduct terrorist activity. Jalaluddin Haqqani consistently placed Mali Khan in positions of high importance."

The Haqqani network was founded by Jalaluddin Haqqani, a warlord who made his name during the 1980s jihad against the Soviets in Afghanistan, when he received funding from Pakistan and the CIA.

Haqqani is a member of the Taliban's supreme council but his son Sirajuddin now effectively runs the network.

ISAF added that Khan had acted as an emissary between the al-Qaeda-linked Pakistani Taliban chief Baitullah Mehsud and Haqqani leaders. Mehsud was killed by a US drone strike in Pakistan in 2009.

A spokesman for Afghanistan's intelligence agency the National Directorate of Security (NDS), Lutfullah Mashal, confirmed the capture but gave different details of his relationship with the network's leader.

"We know that he is a member of Sirajuddin Haqqani's family but we are not sure if he is the immediate cousin. He is maybe the cousin of Sirajuddin Haqqani's cousin," he said.

"I am not sure if he was really an active Haqqani commander," he added, referring media queries back to ISAF.

A senior Western security source speaking to AFP on condition of anonymity said the name of Haji Mali Khan was not familiar as that of a leading insurgent figure.

The Haqqani network has been blamed for a string of attacks in Afghanistan, particularly in the capital Kabul, where US ambassador Ryan Crocker said it was behind a 19-hour attack on September 13 which targeted the American embassy.

In an interview Friday, US President Barack Obama did not endorse Mullen's accusations about Pakistan and the Haqqanis but said Islamabad has "got to take care of this problem".

Meanwhile, the Afghan intelligence service also said it had handed evidence in the case of slain Afghan peace envoy Burhanuddin Rabbani to Pakistani officials.

The NDS has already charged that the killing in September was linked to the Quetta Shura, the Afghan Taliban's leadership body based in Pakistan, although the Taliban have not claimed responsibility for the killing.

"We have submitted all the evidence to the embassy of Pakistan to take action," NDS spokesman Lutfullah Mashal told a news conference.

President Hamid Karzai also said talks with Pakistan were "the only solution" to addressing the insurgency in Afghanistan following Rabbani's killing.

"The only solution, which is also the demand of all people, is that talks be held with the Pakistani side, since all the sanctuaries and safe havens of the opposition are located in that country," he said in comments released late Friday.

Karzai has long stressed that the roots of the insurgency are in Pakistan.