Kabul (AFP) - A Taliban suicide bomber blew himself up near an Afghan military bus in Kabul Sunday, killing four people in the latest attack in the Afghan capital in the final year of NATO combat operations.
Two military officers and two civilians died when the bomber, who was on foot, targeted the bus taking defence ministry staff to work.
The attack followed an improvised explosive device (IED) blast on Saturday evening in which two people were wounded and a massive suicide attack on a restaurant a week ago that killed 21 people, including 13 foreigners.
"There are four dead. Two civilians, one of them female, and two military officers. It was a suicide bombing," defence ministry spokesman General Zahir Azimi said of Sunday's attack.
At least 22 people were also injured, including two other civilians, he added.
A Taliban spokesman using a recognised Twitter account claimed responsibility for the blast in the southeast of the city shortly after 07:00 am.
The militants claimed 27 Afghan troops had been killed or wounded, though they regularly exaggerate death tolls after attacks.
NATO combat forces are withdrawing from Afghanistan this year after more than a decade of fighting the Taliban, but negotiations have stalled over a deal to allow some US and NATO troops to stay after 2014.
President Hamid Karzai on Saturday signalled that talks over the bilateral security agreement (BSA) were close to collapse after he made a surprise decision last year not to promptly sign an agreed text.
Washington has become increasingly frustrated by Karzai's manoeuvreing over the deal, with some US politicians pushing for a complete US pull-out by December.
"Afghanistan will absolutely not accept or sign anything under pressure," Karzai told a press conference on Saturday.
"If they want to leave, then they can go and we will continue our lives... Our main condition is the practical start of the peace process.
"The start of a peace process would mean that no foreigners can benefit from the continuation of war."
The US had earlier wanted the BSA to be signed by the end of October so that the NATO military coalition could schedule the withdrawal of its troops.
About 58,000 NATO-led combat troops who are still in Afghanistan are due to leave by the end of 2014.
Washington is proposing that 5,000 to 10,000 US soldiers are deployed from 2015 to train and assist Afghan security forces in their battle against the Taliban militants.
Afghanistan's fledgling security forces face a difficult year in 2014 as insurgents attempt to disrupt elections on April 5 that will choose a successor to President Karzai, and as NATO's combat mission winds down.
Signing the BSA is also a precondition for the delivery of billions of dollars in Western aid for Afghanistan, but Karzai dismissed suggestions that the aid was essential to future development.
The president has had a tempestuous relationship with the US and other foreign allies since he came to power in 2001, often sparking outrage with his criticism of international efforts to help the country.
A similar US security deal with Iraq collapsed in 2011 leading to a complete troop pull-out and the country is now in the grip of worsening sectarian violence.