At least six people were killed in a suicide car bomb attack in the Afghan capital today, officials said, hours after US president Barack Obama left Kabul following an unannounced visit during which he signed a strategic partnership agreement.
The blast, and Mr Obama's visit, came a year after US special forces troops killed al Qaeda leader Osama bin Laden, the architect of the September 11th, 2001 attacks, in a raid in neighbouring Pakistan.
The Taliban, ousted by US-backed Afghan forces for harbouring bin Laden and other militants, quickly claimed responsibility for what it said was a suicide car bomb attack.
Today's attack was the latest in a recent surge of violence after the Taliban announced they had begun their usual "spring offensive", and that they had suspended tentative steps towards peace talks with the United States.
Kabul police chief Ayoub Salangi said six people, a Gurkha guard and five passers-by, were killed in the Kabul attack.
Mr Salangi told Reuters a car bomb exploded on Jalalabad road, the main road out of the capital heading east, where several US military bases and compounds housing Westerners are located. He said one of those compounds, known as 'Green Village', was the target. A plume of black smoke was seen rising from inside the area.
Witnesses heard a second blast in the same area about 90 minutes after the first explosion.
The interior ministry earlier said at least two people had been killed , and another police official said an exchange of gunfire followed the first blast. Afghan media said heavy casualties were feared.
Taliban spokesman Zabihullah Mujahid said: "One of our mujahideen detonated his car in front of a military base."
"Other mujahideen are inside the base fighting. There are very heavy casualties for the enemy," Mr Mujahid told Reuters by telephone from an undisclosed location.
The Taliban often exaggerate accounts of attacks involving foreign troops or Afghan government targets.
A spokesman from Nato headquarters in the country said the coalition was aware of several explosions.
Mr Obama marked the anniversary of bin Laden' s death with a speedy trip to Afghanistan, signing the strategic pact with Mr Karzai and delivering an election-year message to Americans that the increasingly unpopular war is winding down.
"My fellow Americans, we have travelled through more than a decade under the dark cloud of war," Mr Obama said at Bagram Airfield, where he had arrived about six hours earlier.
"Yet here, in the pre-dawn darkness of Afghanistan, we can see the light of a new day on the horizon."
Most foreign combat troops are due to leave Afghanistan by the end of 2014 under a plan to hand security responsibility to Afghan forces.
Mr Obama left the country about three hours before the explosion, after making a televised address to Americans from Bagram Air Base north of the capital.
A US embassy warning system urged staff to stay away from windows and take cover after the explosion. The embassy is in the main diplomatic area in the centre of the city.
Insurgents staged coordinated attacks in Kabul last month, paralyzing Kabul's centre and diplomatic area for 18 hours.
The Taliban claimed responsibility for those attacks, but US and Afghan officials blamed the militant, al Qaeda-linked Haqqani network.
Reuters/Bloomberg