KABUL, Afghanistan — NATO and Afghan forces captured a senior leader of the al-Qaida- and Taliban-allied Haqqani terror network operating inside Afghanistan, the alliance said Saturday.

NATO announced that coalition forces seized Haji Mali Khan during an operation earlier in the week in eastern Paktia province, which borders Pakistan.

The alliance called it "a significant milestone" in the fight against the terror group.

NATO identified Khan as an uncle of Siraj and Badruddin Haqqani, two of the sons of the network's aging leader Jalaluddin Haqqani.

The Pakistan-based network is affiliated to both the Taliban and al-Qaida and has been described as the most serious security threat in Afghanistan.

In a statement sent to NBC News, NATO said Khan was "one of the highest ranking members of the Haqqani network and a revered elder of the Haqqani clan."

"He reportedly worked directly under Siraj Haqqani, and managed bases and had oversight of operations in both Afghanistan and Pakistan," the statement added. "Mali Khan moved forces from Pakistan to Afghanistan to conduct terrorist activity. Jalaluddin Haqqani consistently placed Mali Khan in positions of high importance."

It said that Khan "submitted to the security force without incident or resistance" even though he was "heavily armed" at the time.

Other insurgents held
"Multiple additional insurgents were detained during the security operation, to include Mali Khan's deputy and bodyguard," the statement read.

It said the Haqqani network and its safe havens remained "a top priority" for Afghan and coalition forces.

"Security forces have conducted more than 500 operations so far in 2011 in an effort to disrupt the Haqqani network leadership, resulting in the death of 20 network facilitators and the capture of nearly 300 insurgent leaders and 1,300 suspected Haqqani insurgents," the NATO statement said.

The Taliban denied that Khan had been captured.

"I have just spoken with Haji Mali Khan, he is fine and is somewhere else and hasn't been detained," spokesman Zabihullah Mujahid told Reuters. "This is a baseless news and it has been released in order to weaken Mujahideen's morale," he said.

Members of the Haqqani network declined to comment on the ISAF statement, but confirmed to Reuters that Khan is Sirajuddin Haqqani's maternal uncle.

Video: U.S. and Pakistan spar over Haqqani network (on this page)

The raid happened on Tuesday in Jani Khel district, a day after President Barack Obama said Pakistan must "take care" of the Haqqani network and its safe havens in Pakistan, amid claims of links between the Haqqanis and Pakistan's intelligence agencies, the AFP news agency reported.

"... my attitude is whether there is active engagement with Haqqani on the part of the Pakistanis or just passively allowing them to operate with impunity in some of these border regions, they have got to take care of this problem," Obama said.

NATO said this year they had arrested 1,300 suspected Haqqani insurgents and 300 insurgent leaders in 500 operations that aimed to disrupt the network. About 20 "network facilitators" were killed, the force added.

Khan had also established a militant camp in Paktia province in the past year, and reported directly to Sirajuddin Haqqani, NATO said.

Sirajuddin is now believed to be in charge of day-to-day affairs of the Haqqani network because his father has health problems.

Before fighting in Afghanistan, NATO said Khan had served as a Haqqani network envoy to Baitullah Mehsud, former leader of the Pakistani Taliban who was killed in 2009.

Assassination evidence
Meanwhile, Afghanistan's intelligence service said Saturday it had given Pakistan hard evidence that former Afghan President Burhanuddin Rabbani's assassination was planned in the southern outskirts of the Pakistani city of Quetta where key Taliban leaders are based.

NBC: Why Pakistan has pushed back on US requests to go after Haqqani network

In the wake of Rabbani's death, the Afghan government has said it no longer thinks negotiations with the Taliban can be productive and that there should be negotiations with Pakistan instead.

The Taliban have not claimed responsibility for killing Rabbani, who headed the Afghan government's effort to broker peace with the insurgents.

A suicide bomber claiming to be a peace emissary from the Taliban killed Rabbani at the former president's home on Sept. 20 by detonating a bomb hidden in his turban.

Rabbani's death was a major setback to U.S.-backed efforts to broker peace with insurgents and end the nearly decade-long war.

On the sidelines of the U.N. General Assembly meeting in New York last week, an Afghan intelligence official said Rabbani's death was plotted for four months by the Afghan Taliban's governing council known as the Quetta Shura, named after the city in southern Pakistan.

Lutifullah Mashal, a spokesman for the Afghan intelligence service, provided the first details about where the assassination was allegedly planned at a news conference on Saturday.

"The place where Professor Rabbani's killing was planned is a town called Satellite near Quetta, Pakistan," Mashal told reporters. "The key person involved in the assassination of Rabbani has been arrested and he has provided lots of strong evidence about where and how it was planned. We have given all that evidence to the Pakistan embassy."

The Afghan intelligence documents handed over to Pakistan's embassy in Kabul include the address, photographs and a layout of a house in Satellite, Mashal said. He said the Pakistanis also have been provided with the names of individuals who discussed Rabbani's assassination at the house in Satellite.

Mashal would not disclose the identity of the person in custody, saying only that he was a second-tier figure within the Taliban hierarchy.