A suicide bomber has killed six Afghan soldiers and wounded 11 others after targeting a bus on the outskirts of Kabul, according to the Afghan Ministry of Defense.

The incident comes after a period of two weeks in which there were almost no serious attacks in the Afghan capital.

Dawlat Waziri, deputy spokesman for the Ministry of Defense, told Reuters that a bomber targeted the bus in the Tarakhil area of the capital's east while the soldiers were travelling to work.

"Unfortunately, we lost six soldiers and 11 others were wounded in the suicide attack," said Waziri.

The Taliban claimed responsibility for the attack and alleged that 12 soldiers had been killed in the bomb blast, a higher estimate than that of the Ministry of Defense.

The blast occurred as foreign troops begin to leave the country and a new unity government begins to take the reins of its security.

Nato troops in Afghanistan will change from a combat role to one of support from 31 December, leaving approximately 12,500 troops, a reduction from the 2010 peak of 130,000.