"Unfortunately, the savage terrorists have committed a cowardly act once again and martyred a patriotic Afghan," interior ministry spokesman Mirwais Stanikzai said of the death of Dawa Khan Menapal.

The Taliban claimed responsibility for the death, with spokesman Zabihullah Mujahid sending a message to media saying "he was killed in a special attack carried out by mujahideen".

Fighting in Afghanistan's long-running conflict has intensified since May, when foreign forces began the final stage of a withdrawal due to be completed later this month.

The Taliban already control large portions of the countryside, and are now challenging Afghan government forces in several large cities.

The militants warned Wednesday of more attacks targeting Afghan government leaders, a day after the defence minister escaped an assassination attempt.

The bomb-and-gun attack on Defence Minister Bismillah Mohammadi Tuesday night brought the war to the capital for the first time in months.

The Afghan and US militaries have stepped up air strikes in their fight against the insurgents in a string of cities, and the Taliban said Wednesday the Kabul raid was their response.