The assassination of a close ally and mentor of Hamid Karzai a week after the killing of the president's powerful half-brother has raised new questions over whether Afghanistan's precarious power structure could collapse even before the departure of western combat troops in 2014.
Jan Muhammad Khan was killed when two gunmen stormed his walled compound in Kabul on Sunday night, holding off Afghan security forces until Monday morning. The attackers also gunned down an MP from Khan's home province, Uruzgan, before being killed themselves.
The assassinations of the two powerful warlords, who once seemed unassailable, have caused widespread shock.
Ahmed Shan Behsad, an Uruzgan MP, said: "These killings show the weakness of failure of Karzai's politics. The situation is crisis. Karzai has lost control of the country."
The Taliban said they carried out the killing, but that could not be confirmed. It is also unclear whether they were behind the death last week of Ahmed Wali Karzai, the president's half-brother, who was shot at close range by his own security chief at his home in Kandahar. A week on, explanations ranged from a vendetta over money to the possibility that the security chief had been "turned" by the Taliban in Pakistan.
The two targets had much in common. Ahmed Wali was the president's closest sibling and the mainstay of his support in Kandahar. Khan was described by some as a surrogate father to the Karzai brothers, and he held similar sway over Uruzgan.
Both men were warlords who had built their power on force and were reported to have amassed fortunes from the drug trade. In the absence of more legitimate institutions, western forces had relied on them to help fight the Taliban. Ahmed Wali ran a paramilitary group called the Kandahar Strike Force, which co-operated with Nato special forces and the CIA.
Khan, another member of the president's Popolzai tribe, had left Uruzgan in 2006 on the insistence of Dutch troops unhappy with his drug-running, but his influence persisted. His nephew, Matiullah, runs a private army in Uruzgan that helps fight the Taliban and protects Nato convoys for cash. Khan was believed to have helped the US target suspected Taliban fighters – and his rivals.
Thomas Ruttig of the Kabul-based Afghan Analysts Network wrote on Monday: "With his rivals, [Jan Muhammad Khan] dealt ruthlessly. He labelled them Taliban, and sent the special forces after them – who misinterpreted their mandate to support the 'central government' as supporting one man against his personal rivals and who appreciated his qualities as an effective Taliban hunter."
Two months ago a key Karzai ally in the north, police chief Muhammad Daoud Daoud, was killed in Takhar province by a Taliban suicide bomber who infiltrated a meeting between local officials and Nato officers.
The spate of high-profile assassinations has come amid a string of other killings of figures within the country's informal power structure – a network of establishment figures, warlords and drug-runners. Cumulatively, observers say, the killings have sapped Hamid Karzai's political strength and undermined his ability to withstand a Taliban onslaught when western troops leave.
Gerard Russell, a former British diplomat to Afghanistan, said: "The balance of power is being radically destabilised, and central government is losing any prospect of wielding authority. The targets are really the linchpins of the post-2001 security settlement, and they are being pulled out one by one. So it's even more serious that it looks. Afghanistan has been built on building blocks like these."
Khan's killing coincided with departure of General David Petraeus, the architect of Nato's military strategy in Afghanistan, to become CIA director in Washington, and came a few hours after a ceremony on Sunday to mark the start of transition from Nato to Afghan-run security in the first Afghan province, Bamiyan. A similar handover will be marked this week in Lashkar Gah, the British-garrisoned administrative centre of Helmand province, where seven Afghan policemen were killed at a checkpoint on Monday.
The transition is due to be completed by the end of 2014, when all western combat troops are due to have left. However, several observers said that the spate of killings of Karzai relatives and lieutenants raised doubts that the president's authority would hold up that long.
"The biggest thing is the psychological impact on Karzai losing two people very close to him and to the family," Ruttig said. "In a system here that is very patronage-based, that he is not able to protect his closest allies will have consequences. People will hedge their bets, in case the Taliban come back one day. They will make deals so they can survive that. With the first western soldiers leaving there is an atmosphere of concern and fear. People sending their sons out of the country to study or giving money so smugglers can take them abroad … they don't trust that the institutions are sustainable enough to survive."