The latest bombing came during a memorial ceremony for a Canadian soldier killed the day before. An Afghan bystander also died in that attack. The Taliban once more claimed responsibility.
The British soldier died after a taxi packed with explosives detonated near his patrol vehicle at about 11 a.m. local time near the main British base in the eastern outskirts of Kabul, said Nayamatullah Jalili, intelligence chief at the Afghan Interior Ministry. He said an Afghan was also killed - apparently the assailant.
"The preliminary investigation suggests it was a suicide attack," Jalili told reporters after visiting the scene.
In London, the British Ministry of Defense said another four soldiers were wounded, though there was no word on their condition.
The Canadian deputy commander of the peacekeeping force, speaking at the memorial ceremony, initially suggested a second blast had occurred at a German base nearby. But a spokesman for the force, Lt. Col. Joerg Langer, said there was just one explosion.
Capt. Tom Smith, a spokesman for the British contingent in Kabul, said a taxi was apparently involved in the Wednesday attack, but declined to comment further.
There were no reports of civilian casualties.
International troops and Afghan authorities quickly closed off the scene of the attack on the British patrol.
From nearby, a Land Rover jeep of the type used by British forces here could be seen in the debris-strewn road, the front of the vehicle ripped open and badly charred.
The blast blew out the windows of a bathhouse nearby, sending people scurrying from the showers, said Zulgai, 20, a worker there who like many Afghans uses only one name.
"It was a very strong sound," Zulgai said.
Mullah Hakim Latifi, who claims to speak for the Taliban, said they had orchestrated the attack.
"We are compelled to attack the foreigners to defend our country, religion and honor," he said in a satellite telephone call to The Associated Press.
His claim couldn't be independently verified.
Latifi had also claimed Taliban responsibility for Tuesday's attack and alleged it would be the start of a campaign of suicide bombings across the country. That attack wounded three Canadian troops and eight civilians, including a Frenchman, when the bomber struck the Canadian patrol.
At Wednesday's memorial, the new blast was heard during the ceremony that took place as a heavy snowstorm buffeted the city.
The escalating violence comes the same week that President Hamid Karzai signed the country's post-Taliban constitution into law, with hopes that it can help bring the fractured country together after more than two decades of war.
By Amir Shah