Afghan officials say gunmen have shot and killed a senior member of the Afghan peace council, dealing the latest blow to peace negotiations.

Authorities say an unidentified gunman in a car opened fire on Arsala Rahmani Sunday morning in Kabul as he was on his way to work.

Rahmani was a former Taliban official who became a top member of the Afghan peace council set up by President Hamid Karzai to negotiate a peaceful end to more than 10 years of war. He served as deputy minister of higher education during the Taliban's rule in Afghanistan.

The Taliban has denied responsibility for the attack.

Meanwhile, Afghan officials say they are taking the lead from the international coalition for providing security in areas that make up 75 percent of the country's population.

The Afghan government announced Sunday that it was launching the third phase of the transition of military control.

The first two phases already have put Afghans in control of areas representing half of the country's population. The final stage is set to be completed by the end of 2014, when most foreign combat troops are scheduled to leave.

The U.S.-led International Security Assistance Force in Afghanistan reacted to the killing of Rahmani by saying he “chose to make a positive contribution to his nation by turning his back on an insurgent movement” that continues to be detrimental to the future of Afghanistan. An ISAF statement said the attack “is clear evidence” that those against the Afghan government have “no interest in supporting the peace process on any level.”

Last September, former Afghan president Burhanuddin Rabbani — who was the head of Mr. Karzai's peace council — was assassinated by a suicide bomber.