At least four Afghan soldiers were killed and around a dozen people including six civilians wounded when a roadside bomb planted by the Taliban exploded in the Afghan capital on Tuesday.

At least four Afghan soldiers were killed and around a dozen people including six civilians wounded when a roadside bomb planted by the Taliban exploded in the Afghan capital on Tuesday, officials said.

The blast, caused by a remote-controlled bomb, targeted an Afghan army bus in the western part of Kabul, the Ministry of Defense said.

"In a remote-controlled bomb attack against an army bus at 6:45 am local time (02:15 GMT) in Aqa Ali Shams in Kabul, four army personnel were killed and 12 wounded, including six civilians," the ministry said in a statement.

The Taliban, who have this year stepped up their attacks against the Afghan security forces, claimed responsibility via their official Twitter account.

Taliban terrorists killed six Afghan police last Tuesday in the Logar province south of Kabul, a day after insurgents ambushed a convoy in the north and killed 22 policemen.

The inauguration of new President Ashraf Ghani last month was also marred by a spate of suicide attacks on security forces killing more than a dozen people.

The U.S. military estimated this month that 7,000-9,000 Afghan police or troops had been killed or wounded so far this year.

Ghani, who was sworn into office last month following a lengthy election process, has signed a long-delayed agreement allowing about 13,000 foreign troops to stay on into 2015.

But the follow-up mission, which will take over on January 1 -- 9,800 U.S. troops and about 3,000 soldiers from Germany, Italy and other NATO members -- will focus mainly on training local forces and counter-terrorism operations.