Earlier, leaders of the group Monday said unidentified gunmen shot Naseeruddin dead late Sunday night near Pakistan's capital Islamabad when he was returning home from a mosque, reported Xinhua.
The gunmen, riding motorcycles, fled after the attack, police sources and witnesses said.
Spokesman for Tehrik-e-Taliban Pakistan (TTP) Shahidullah Shahid confirmed the killing of Naseeruddin Haqqani.
"We will take revenge of the murder," the TTP spokesman said.
"The dead body was later sent to North Waziristan tribal region and buried there," a Haqqani Network official said.
Slain Naseeruddin Haqqani was responsible for fund-raising, logistics and political affairs of the Haqqani Network, the network sources said.
Islamabad police confirmed the firing incident but did not say anything about identity of the man.
Eye witnesses said the slain man arrived in the market in his car with the driver to buy bread from a shop in a small market on Simly Dam road in Barakau.
A witness said the gunmen, riding motorcycles, arrived and started firing at him as he was waiting to buy bread from a shop.
A young man working in the shop was also injured when the gunmen sprayed dozens of bullets. He was taken to a hospital and is under treatment.
No one has claimed responsibility for the assassination.