KABUL, Afghanistan — Mullah Arsala Rahmani, a former Taliban minister who was an important go-between in potential peace talks, was shot and killed Sunday as he headed to a government meeting on reconciliation, Afghan officials said.

Mr. Rahmani, who lived openly in Kabul under close protection from the Afghan intelligence service, the National Directorate of Security, was killed in his car by a gunman who then escaped, said a fellow member of the High Peace Council, Muallawi Shafiullah Nuristani.

“His assassination is a big loss,” Mr. Shafiullah said. “It will affect the peace process because he played an important role in mediating the peace talks and was a trusted person among the Taliban.” Mr. Rahmani had been the minister of higher education during Taliban rule and was known as a relative moderate.

A spokesman for the Taliban, Zabiullah Mujahid, reached by telephone, said they were not responsible for the killing. Although Mr. Rahmani often acted as an informal spokesman for the Taliban during peace talks, the insurgents had disavowed him as an interlocutor. The Taliban had threatened to kill members of the High Peace Council as part of their spring offensive, according to local news reports.

In September, a Taliban emissary to the High Peace Council hid a bomb in his turban and assassinated the leader of the council, Burhanuddin Rabbani, a former Afghan president.

“It is true that at the beginning of our spring operation we announced that among many other entities and individuals we will target members of the so-called High Peace Council,” Mr. Mujahid said, “and we are still committed to our campaign against the so- called members of the so-called High Peace Council, but again I insist that the Taliban were not behind today’s assassination.”

Wahid Mojdah, a former Taliban official who is a political analyst in Kabul, said he thought it was unlikely that the Taliban had killed Mr. Rahmani. “He had never done anything to make the Taliban angry,” he said.

“He was playing an important role in convincing the Taliban and the Haqqanis to moderate their stance on schools and education,” Mr. Mojdah added, referring to the Haqqani faction of the Taliban. “The fact that he was shot dead in front of his house while he was surrounded by his bodyguards raises a lot of questions.”

Mr. Rahmani was attacked just after he left his heavily guarded home in western Kabul to attend the inaugural meeting of a new government body, said an Afghan police official who spoke on the condition of anonymity because the death was still being investigated. It was unclear if anyone else had been killed in the attack.

The meeting of the new government body, the High Council of the Independent Commission for Dispute Resolution and People-to- Government Relations, had been announced Saturday; after the attack, it was canceled.

Efforts to start peace talks with the Taliban have faltered in recent months as the Taliban disavowed them, and a smaller insurgent group, Hezb-i-Islami, which had already been in discussions with the Afghan government, announced that it was pulling out as well.

There had been plans for the Taliban to open a political office in Qatar and for the United States to release Taliban prisoners from detention at Guantánamo Bay, Cuba, to the custody of the government of Qatar. The release of an American, Sgt. Bowe Bergdahl, held by the Taliban was also under discussion.

On “Fox News Sunday,” Senator Dianne Feinstein, chairwoman of the Select Committee on Intelligence, said Pakistan was crucial to defeating the Taliban and expressed frustration that Pakistan had failed to deprive the insurgents of a haven in the rugged mountains along its Afghan border.

“Militarily, I think that the Taliban are not going to beat us,” said Ms. Feinstein, a Democrat from California. But the Taliban “have a safe harbor in Pakistan, and the Pakistanis are doing nothing to abate that safe harbor.”

Also on Sunday, the Afghan government announced the beginning of the third phase of the transfer of security authority from international to Afghan forces, a process scheduled to be complete by 2014.

At a news conference, Aimal Faizi, the spokesman for President Hamid Karzai, said this stage would place 75 percent of Afghanistan’s population under the protection of the country’s police and military forces. The transition will now include parts of all 34 provinces, a statement from Mr. Karzai said.

The announcement came a week before a NATO summit meeting in Chicago intended to determine the allies’ future commitments in Afghanistan.

The NATO-led International Security Assistance Force also announced that an improvised bomb killed two service members in eastern Afghanistan on Sunday. No details were available. Habib Zahori and Graham Bowley contributed reporting. (Copyright 2012 The New York Times Company 05/14/12)