bombing in the morning..

At least 13 people have been killed by a suicide car bomb attack in the Afghan capital, Kabul, the defense ministry has said.

The bomber hit a bus carrying Afghan soldiers during morning rush hour in the south-west of Kabul.

The defense ministry said six soldiers and seven civilians were killed and a dozen other people were injured.

The blast comes one day after a similar attack on a Nato convoy close to Kabul airport injured 22 Afghans.

The number of dead is expected to rise as several of the wounded have been severely injured.

Witnesses said the bomb was in a small car that drew up close to the bus before exploding shortly early on Wednesday.

The bus carrying the soldiers was destroyed in the explosion.

Target

The BBC's David Loyn in Kabul says buses carrying soldiers and police have increasingly been the target of suicide bombers in recent weeks.

The bombing is the third suicide attack in the city in the last eight days.

US Defence Secretary Robert Gates is in Kabul assessing an increase in violence in Afghanistan.

He said the increase was partially due to an offensive against Taleban militants by international troops from the Nato-led International Security Assistance Force (Isaf).

Afghan military officials say they need more training and equipment to fight the growing Taleban insurgency.