One of the most senior leaders of the Haqqani militant network has been shot dead near the Pakistani capital, Islamabad, security sources say.

Nasiruddin Haqqani, who was in his early 30s, was the group's financier and a son of its founder Jalaluddin.

Reports say his body has been taken for burial to the North Waziristan tribal area near the Afghan border.

It is not clear who shot him or why. Nasiruddin Haqqani was on a US list of global terrorists.

The details of his death are still unclear, but reports say he was killed in a shooting incident in the city of Rawalpindi, next to Islamabad, on Sunday night.

Security sources confirmed the killing to the BBC.

Other reports quoted militant sources and witnesses, who said unidentified gunmen on motorbikes sprayed Haqqani with bullets as he stopped to buy fresh bread from a bakery in the north-eastern outskirts of the capital.

Another Haqqani brother, Badruddin, who had been the group's operational commander, was killed in a drone strike in August last year.

Nasiruddin's elder brother, Sirajuddin Haqqani, now leads the group, while Jalaluddin remains its figurehead.

As the group's main fundraiser, Nasiruddin frequently travelled to the oil-rich sheikhdoms of the Middle East to solicit donations.

Image caption Jalaluddin Haqqani (right) is seen here as Taliban minister of tribal affairs in 2001

He represented the Haqqani network in last year's efforts to set up a Taliban office in Doha for peace talks with the United States.

He was also the group's main contact person for pro-Taliban elements in Pakistan, as well as its representative with the Afghan Taliban.

'Well-dressed networker'

Unlike his father and many of his brothers, Nasiruddin Haqqani and two of his uncles did not live in Miran Shah in North Waziristan. He chose to base himself near Islamabad, from where he made his many journeys abroad to secure funds.

Some sources said he had major business interests in the Gulf, including a transport company.

Nasiruddin is not thought to have been publicly photographed.

Those who have met him describe a tall, educated, well-dressed man who travelled in expensive cars and networked an extensive list of contacts all the time.

They say his appearance gave no clue to his militant connections. His code name was "the doctor", possibly because of a degree that he had studied for.

His death will be a major blow to the Haqqanis, who will need to find someone else to spearhead their efforts to secure financing.

BBC correspondents say the killing will pile pressure on the Pakistani government because Nasiruddin's death happened on Pakistani soil.

Afghan authorities will be angry that someone who had been working to facilitate peace moves with the Afghan Taliban has been removed from the picture.

His death comes just 10 days after a US drone killed Pakistani Taliban leader Hakimullah Mehsud, who was also reported to be on the verge of entering peace talks with the government in Islamabad.

Those moves towards talks are now over. His successor, the more hardline Mullah Fazlullah, swiftly ruled out any negotiations.

Attempts to begin talks between the US, the Afghan Taliban and the government in Kabul have been stalled since June.