US drone strikes killed a prominent warlord who had sent insurgents to fight in Afghanistan as well as nine other militants in Pakistan's tribal belt, according to local officials.

Mullah Nazir was the main militant commander in South Waziristan, part of the tribal zone where militants linked to the Taliban and Al-Qaeda have bases. He is one of the highest-profile drone victims in recent years.

Pakistani officials said a US drone fired two missiles at his vehicle in the Sar Kanda area of Birmil in South Waziristan, and five of his loyalists including two senior deputies were also killed.

"Mullah Nazir and five associates died on the spot," one of the officials told AFP on condition of anonymity.

The official said the attack happened at 10:35 pm on Wednesday (1735 GMT) but that it took time to confirm the reports from such a far-flung and mountainous area along the Afghan border.

Another Pakistani official said Nazir and his fighters were targeted as they prepared to swap vehicles when their pick-up encountered a mechanical fault.

Two of his influential deputies, Atta Ullah and Rafey Khan, were among those killed, the official added.

Local residents later told AFP that funeral prayers were said for Nazir and his associates around 10 kilometres (six miles) west of Wana, the main town in South Waziristan, and markets and shops closed.

In the neighbouring district of North Waziristan, two more missiles fired from a US drone killed four other militants on Thursday but their identities were not immediately known, other Pakistani security officials said.

Although Nazir's fighters have long been targeted by US drone strikes, he reached a peace deal with Washington's ally Islamabad in 2007 and had testy relations with the Pakistani Taliban, who are fighting a domestic insurgency.

He was wounded in a suicide attack in South Waziristan on November 29 and had survived previous attempts on his life.

Nazir was understood to be close to the Al-Qaeda-linked Haqqani network, a faction of the Afghan Taliban blamed for some of the most high-profile attacks in Kabul and elsewhere in Afghanistan in recent years.

Analysts were divided on the impact that his death would have on Pakistan and on the US-led war against an 11-year insurgency in neighbouring Afghanistan.

Pakistani author and expert on the tribal belt, Imtiaz Gul, suggested there would be little fallout for Pakistan, which is trying to assist efforts by the Western-backed Kabul government to broker a peace deal.

"The Americans and Afghans suspected Mullah Nazir of sheltering and hosting Arab Al-Qaeda operatives," Gul told AFP.