The bus carrying police recruits and trainers exploded outside police headquarters, in a crowded part of the city.
"The explosion shook the area," an unidentified eyewitness told RFE/RL. "We immediately went out and saw that the smoke was coming out from opposite the main police headquarters. People were fleeing the scene. Being afraid of another explosion we did not get close to the site of the incident."
Police And Civilians
The chief of Kabul's criminal investigation department, Ali Shah Paktiawal, told an RFE/RL correspondent that the victims included both police and civilians.
"In this blast, which took place around 8:00 a.m., many people were injured," Paktiawal said. "But 35 people, including policemen and ordinary people, were martyred."
A spokesman for Interior Ministry, Zemarai Bashari, confirmed the death count and suggested it was a suicide attack.
"The final reports say that 35 people have been killed and some 52 others were injured in this suicide attack," Bashari told RFE/RL. "Some civilians are also among them, but for the time being I can't say the exact number of the civilian casualties. It is said that it has been a suicide attack. The [suicide bomber] has attacked the bus and then exploded himself."
However, it remains unclear whether the blast was in fact caused by a suicide bomber. Police officials have said that one person could not have carried enough explosives to trigger such a powerful explosion.
Police said they were looking into reports that a bomb may have been placed on the bus.
A purported spokesman for the insurgent Taliban movement, Qari Yousef Ahmadi, said one of its members caused the blast. Ahmadi said the bomber was named Mullah Asim Abdul Rahman.
The claim could not be independently verified.
Deadly Statement
The death toll of 35 makes the bus blast the deadliest such insurgent attack in Afghanistan since the fundamentalist Taliban regime was driven from power in 2001.
At least 20 of the dead were confirmed to be police officers and trainers who were on their way to a police academy in the city.
It remains unclear whether the blast was caused by a suicide bomber (RFE/RL)