KABUL, Dec. 15 (Xinhua) -- A deputy to the provincial governor and his office assistant were killed and two people were wounded in a bomb explosion, hitting an official vehicle in Kabul, capital of Afghanistan on Tuesday, an Interior Ministry official confirmed.

"Mahbubullah Muhibi and his office assistant were martyred following an explosion Tuesday morning after an improvised sticky bomb attached to his vehicle was detonated. Two security guards aboard the vehicle were wounded," Tariq Arian, spokesman of Interior Ministry, told Xinhua.

The four-wheel-drive vehicle was severely damaged by the force of the explosion roughly at 9:40 a.m. local time along a lane near a corner in Makroryan-e-Char locality, the official said, adding that the initial information found that an improvised bomb was attached to the vehicle.

An investigation has been launched in the case, according to Arian.

No group has claimed responsibility for the attack yet. Afghan officials accused Taliban militants for the targeted attacks as militants' infiltrators have conducted scores of targeted attacks in big Afghan cities in recent months.

Earlier on Tuesday, a police officer was killed and two police wounded in a gun shooting in Butkhak locality in Police District 12, in the eastern part of Kabul when armed militants fired on them roughly at 6:30 a.m. local time.

Civilians considered to be supporting the government, civilian government employees, religious leaders, tribal elders and persons involved in peace and reconciliation efforts have come under attack in targeted killings over the past years.

About 44 people lost their lives and many others were wounded in targeted attacks across Afghanistan in November, according to the official figures.