KABUL, Afghanistan — A suicide bomber rammed a sedan full of explosives into a packed commuter minibus in Kabul on Monday, according to Afghan officials and eyewitnesses.

It was the second serious attack in the capital in less than a week. Gunmen stormed the main military hospital on Wednesday, killing at least 31 people, many of them patients shot in their rooms.

Two eyewitnesses to the attack on Monday, one of them an off-duty policeman, said that a Toyota Corolla smashed into the minibus and exploded, engulfing the minibus in flames and burning everyone inside.

Other accounts said that a roadside bomb may have been involved.

It was not immediately known how many people were in the minibus. The vehicles are commonly used to take government employees and other workers home, and sometimes carry as many as 20 people.