ISLAMABAD — The chief financier of the Taliban-linked Haqqani network militant group has been shot dead in the Pakistani capital of Islamabad, militant sources told Reuters on Monday.

"Nasiruddin Haqqani was killed in Islamabad while traveling in a car with a few other unidentified people," one Taliban source said, adding that the attack took place on Sunday. "His body has been moved to North Waziristan."

In June 2010, the United States Treasury sanctioned Nasiruddin and two other Afghans as "specifically designated global terrorists" for their work as senior leaders and financiers for the Taliban and the affiliated Haqqani network.

The United States has also branded the Haqqani network, a group U.S. officials blame for high-profile attacks in Afghanistan, as a terrorist organization in September 2012.

Pakistani police and government officials were not immediately available for comment.

The deceased Nasiruddin Haqqani was the elder brother of Sirajuddin Haqqani, the guerrilla commander who heads the Haqqani network and has directed some of the most brazen attacks against U.S. forces in Afghanistan.

Taliban sources confirmed that Haqqani's body had been moved to North Waziristan, the stronghold of the Taliban insurgency, which shares a border with Afghanistan.

"His funeral is scheduled for 4 p.m. today in the Miranshah area," a source said, referring to the regional capital.

The Haqqani network is named after the brothers' father, Jalaluddin Haqqani, a veteran guerrilla commander from southeast Afghanistan who rose to prominence battling occupying Soviet forces in the 1980s.