Updated

Gunmen on the outskirts of Islamabad shot dead a senior leader of one of the most feared al Qaeda-linked militant groups fighting U.S. troops in Afghanistan, a Pakistani Taliban commander and an intelligence official said Monday.

Nasiruddin Haqqani, a key financier of the Haqqani network, was gunned down by armed men riding a motorcycle on Sunday night in a residential area called Bhara Kahu, which is only a couple miles from the U.S. Embassy.

He had stopped to buy fresh bread at the local bakery, said Tanveer Ahmed, who was nearby when the shooting occurred but only learned the dead man's identity later. The attack left blood stains on the pavement and bullet holes in the bakery's tiled wall.

The Haqqani network is a key ally of the Afghan Taliban and has pledged allegiance to its leader, Mullah Omar, though it operates fairly independently. Nasiruddin's presence in the Pakistani capital could raise questions in Washington. U.S. officials have accused Pakistan's intelligence agency of supporting the Haqqani network as a key proxy in the Afghan war -- an allegation denied by Islamabad.

No one has yet claimed responsibility for the killing, but it will likely spark suspicion in Pakistan that the Americans took him out.

Nasiruddin's death comes less than two weeks after the United States outraged Pakistani officials by killing Pakistani Taliban leader Hakimullah Mehsud in a drone strike a day before the government planned to invite him to peace talks.

After the shooting, Nasiruddin's body was taken to the town of Miran Shah in the North Waziristan tribal area -- the Haqqani network's main sanctuary in Pakistan -- where he was expected to be buried Monday afternoon, the Taliban commander, Ahsanullah Ahsan, and the intelligence official said.

Two members of the Haqqani network also confirmed that Nasiruddin was killed. The Haqqani militants and the intelligence official spoke on condition of anonymity because they were not authorized to talk to media.

Nasiruddin was considered an important financier and emissary for the Haqqani network, which is currently led by his brother, Sirajuddin Haqqani. Their father, Jalaluddin Haqqani, founded the group and is well-known for fighting the Soviets after they invaded Afghanistan in 1979.

The U.S. Treasury slapped sanctions on Nasiruddin in 2010 when it added him to its list of specially designated global terrorists. The Treasury said Nasiruddin, who is known to speak Arabic, has traveled to Saudi Arabia and the United Arab Emirates to raise money for the Haqqani network, al Qaeda and the Taliban.

The U.S. has repeatedly demanded that Pakistan carry out an operation in North Waziristan to target the Haqqani network and other militants based there who conduct cross-border attacks against American troops in Afghanistan. The group is blamed for some of the most high-profile attacks in Afghanistan, especially in the capital, Kabul.

Pakistan has refused to conduct an offensive, saying its troops are stretched too thin fighting domestic militants at war with the state. But analysts widely believed that Pakistan is reluctant to cross the Haqqani network, believing it will be a key ally in countering the influence of archenemy India in Afghanistan after foreign forces withdraw.

The U.S. has instead resorted to targeting Haqqani militants and their allies in North Waziristan with dozens of drone attacks, sparking tension with Islamabad.

Pakistani officials regularly criticize drone strikes in public as a violation of the country's sovereignty, but the government has been known to support at least some of the attacks in the past, especially ones targeting enemies of the state rather than groups like the Haqqani network.