Gunmen killed a former Taliban leader who renounced the extremist regime after it was ousted in 2001 and had since supported Afghanistan's US-backed government, officials said.
In a spate of other violence blamed on holdouts from the former regime, 10 people were killed and 41 wounded -- 40 of them in two bombings targeting people celebrating the Islamic feast of sacrifice, Eid al-Adha.
Two men on a motorbike shot Mohammed Khaksar, the former Taliban deputy interior minister, in the heart and head as he was walking with two of his children on Saturday in the southern city of Kandahar, a former Taliban stronghold, police chief General Abdul Wahid said.
Khaksar secretly contacted the Washington in 1999 to seek US help in stopping the Taliban and renounced the movement after its collapse. Last September, he ran as a candidate in legislative elections but lost.
In an interview at the time, Khaksar said Taliban rebels had threatened his life several times. He said he supported Afghan President Hamid Karzai, as well as the deployment of international forces in the country.
A purported Taliban spokesman, Qari Mohammed Yousaf, called The Associated Press to claim responsibility. Yousaf's exact ties to the insurgents' leaders is not known.
"He was a traitor to our cause," he said. "We will kill all Taliban members who do this.''
The killing is believed to be the first of several former Taliban leaders who have swapped sides. The government has encouraged Taliban members to go through a formal reconciliation program and so far, about 300 rank-and-file members and some 50 senior officials have done so.
The shooting comes after the deadliest year in rebel violence since 2001, with some 1,600 people killed, which has raised fears for Afghanistan's nascent democracy.
Militants on Friday fired on a joint Afghan-US patrol and an ensuring battle killed six rebels, military spokesman Lieutenant Colonel Jerry O'Hara said.
The fighting occurred in southern Uruzgan Province, where the Netherlands has delayed a decision to send up to 1,400 troops because of fears they may face stiff violence.
In a second clash, militants attacked an Afghan army checkpoint in eastern Paktia Province on Saturday, the Afghan Defense Ministry said. One soldier and two suspected Taliban rebels were killed.