The daylong funeral observances for Burhanuddin Rabbani, a former president, brought Afghanistan's capital to a near-standstill, with some of the heaviest security in recent memory.
Police and soldiers in armored vehicles patrolled the streets, checkpoints dotted major boulevards and traffic circles, and a large part of central Kabul was blocked to all but foot traffic. Helicopters buzzed overhead.
Rabbani was the head of the High Peace Council, set up by the government a year ago to try to open negotiations with militants of the Taliban movement.
He was killed Tuesday in his home in an affluent Kabul neighborhood by an assailant who claimed to be carrying a peace message from the Taliban leadership, but instead had a bomb concealed in his turban.
Karzai and other senior Afghan officials have described the assassination plot as an elaborate ruse, months in the making. But some of Rabbani's prominent supporters turned their anger against Karzai, who had urged the 70-year-old politician to meet with the man who turned out to be his assassin.
Mourners also shouted slogans denouncing Pakistan, which is seen as fomenting insurgent violence, and the United States, which is also trying to open channels to the Taliban.
The ugly public quarrel that broke out Friday has its roots in Afghanistan's fractured ethnic politics. Like many of his supporters, Rabbani was an ethnic Tajik; Karzai is a member of the sprawling Pashtun ethnic group, from which the Taliban movement is largely drawn.
Rabbani was a leader of the Northern Alliance, the militia that helped drive the Taliban from power in 2001; many of his supporters remain deeply mistrustful of the Taliban and oppose peace negotiations.
The funeral observances began quietly with a solemn prayer ceremony at the heavily guarded presidential palace, where Karzai presided, describing Rabbani as a martyr to the cause of peace. Diplomats and dignitaries paid their respects before the flag-draped coffin.
But things took a chaotic turn when the coffin was moved to a sunbaked hillside overlooking the city for burial. Police and soldiers, apparently trying to maintain order, at first blocked entry for some of Rabbani's supporters, including two prominent politicians who are Karzai's bitter rivals and critics.
One was Amrullah Saleh, who was fired by Karzai as chief of Afghanistan's main intelligence service, the National Directorate of Security. Saleh managed to push his way into the walled compound surrounding the burial site.
Amid the melee, guards fired shots into the air to keep back some of Rabbani's supporters, but eventually allowed the crowd to surge in.
"A terrorist was allowed to enter and kill our leader, and we are not allowed to attend his burial!" Saleh called out, according to a pool report filed by the Reuters news agency. Most journalists were barred from the burial.
As guards tried to quiet him, Saleh told them furiously: "If I ask them [Rabbani's supporters], your government will be destroyed by noon."
More heated rhetoric came from Abdullah Abdullah, Karzai's onetime foreign minister who was his chief rival in 2009's fraud-tainted presidential election. Organizers turned off the microphone when he tried to address the riled-up crowd.
"We buried our leader, but won't be silenced," he said, raising his voice to be heard. "Karzai has to answer to the people and explain who is the killer."
The leadership of the Taliban, which has claimed responsibility for many other political assassinations, disavowed knowledge of Rabbani's killing, saying it was investigating. Police have not yet concluded which insurgent faction might be responsible.
Outside the gates of the burial compound, some Rabbani backers threw stones at guards, and chants of "Death to Karzai!" broke out. Rabbani's son Salahuddin appealed for calm, but also called on the government to investigate the circumstances of the killing.
Karzai was not at the burial; neither were most members of his government.
More unrest was likely Saturday, when a prayer service is scheduled at a central Kabul mosque. Saleh, the fired intelligence chief, issued a thinly veiled appeal for a widened campaign of antigovernment protests.
"The government is not taking responsibility for the shedding of our people's blood. The government doesn't have the right to talk with enemies anymore," he said. "Nothing will come of so much talking. Just wait for a call. Very soon we will come to the streets."