A gunman assassinated the powerful brother of Afghan President Hamid Karzai on Tuesday, striking a blow to stability in the strategic southern province of Kandahar which he governed.
The Taliban claimed responsibility for the killing of Ahmed Wali Karzai, who was gunned down in his home by a man identified as Sardar Mohammad, according to AFP news agency.
Officials described Sardar as a close friend of the controversial southern power broker.
"He was visiting Wali in his home. They were meeting alone in a room, and he gets his pistol and shoots him dead and other bodyguards rush to the room and kill Sardar," a senior intelligence official told AFP on condition of anonymity.
"Wali knew him from a long time ago."
The gunman was shot dead at the scene by Karzai's bodyguards, AFP reported.
But Abdul Ghafar Sayedzada, head of the ministry's counter-terrorism department, told Reuters the killer was a member of Karzai's security team.
"It appears Ahmed Wali Karzai has been killed by one of his bodyguards, and there was nobody from outside involved," he said.
President Karzai expressed sorrow over the murder, which came as he prepared to meet visiting French President Nicolas Sarkozy in Kabul.
"My younger brother was martyred in his house today. This is the life of all Afghan people, I hope these miseries which every Afghan family faces will one day end," President Karzai said at the start of a news conference with Sarkozy.
Ahmed Wali Karzai was the head of the provincial council in Kandahar, the Taliban's southern heartland, and as such represented the shaky writ of the US-backed central government in a key battlefield in the Afghan war.
But he was seen by many as a deeply compromised figure, with alleged connections to Afghanistan's opium trade and questionable links to private security firms.
U.S. diplomatic cables released by whistleblower website WikiLeaks last year portrayed him as a drugs kingpin, suggesting Washington had preferred to keep what it knew of his activities quiet rather than upset President Karzai or rock the boat in Kandahar.
Ahmed Wali Karzai denied all the allegations.
The former Chicago restaurateur and younger half-brother of the president had survived two other assassination attempts in recent years, Reuters reported.