A bomb attack on an Afghan police bus in Kabul has killed up to 35 people and injured more than 30 others.
Police said a number of civilians are among those killed in the rush-hour attack close to police HQ in the city centre. Five foreigners were wounded.
It is thought to be the most devastating bomb attack in Kabul since the Taleban were ousted in 2001.
Taleban rebels told the BBC that they had carried out the attack - the fifth bombing in three days.
The blast site resembled a scene from Baghdad, the BBC's John Simpson says.
Such an attack is disturbingly new on the streets of Kabul and the tactics appear to have been borrowed directly from Iraq, our world affairs editor reports from Kabul.
MAJOR BOMB ATTACKS
17 June 07: Attack on Kabul police bus kills at least 21
27 February 07: Suicide bomber kills 22 at Kabul's Bagram air base during a visit by US Vice-President Dick Cheney
8 September 06: Suicide car bombing in Kabul kills 18 including two US soldiers
1 June 05: Suicide bomber dressed as policeman kills 20 at a Kandahar mosque
In a separate incident later, a roadside blast hit a US-led coalition vehicle in southern Afghanistan, killing three soldiers and their Afghan interpreter, a statement said.
The attack occurred in the southern province of Kandahar, the coalition statement said, without disclosing the nationalities of the soldiers.
Earlier, a suicide bomber on a motorcycle attacked a military convoy in the north Afghan city of Mazar-e-Sharif. One Afghan civilian was killed and several injured but no soldiers were hurt.
'Fire and dust'
Outside police headquarters, there were little pools of blood and bits of bodies.
Wali Mohammad, an eyewitness who was driving his car just behind the bus, told AP news agency he had seen "a big fire and dust" in front of him.
Correspondents say the thunderous blast could be heard across Kabul.
Most of those killed were police instructors. Some of those injured are in critical condition.
Police said two Japanese, two Pakistanis and a Korean national are among the injured.
Sunday was to see the handover of police training in Kabul from Germany to the European Union, Afghan media reports say.
Police say they are uncertain whether the explosion was caused by a suicide bomber - as the Taleban say - or a device placed on board beforehand.
According to AP, the explosion appeared to have happened in the front of the vehicle, which was more badly damaged.
Reuters quotes an unnamed police eyewitness as saying he had seen the bomber leap on to the bus as it was moving slowly away, its door wide open.
The city saw another suicide attack at exactly the same time on Saturday morning. That incident on the outskirts caused at least three deaths.
The past two days have also seen suicide attacks in the north and south of the country.