Nine military officers have been sacked over last month's attack by militants on the military hospital in Kabul, the Afghan defence ministry says.

Those dismissed include a general and a colonel. All face prosecution for negligence, the ministry said.

The attack was one of the worst in the conflict-hit nation in recent months.

About 50 people are said to have died as militants armed with guns, grenades and knives targeted patients and staff at the hospital.

The brutal assault caused shock and anger among the public. Many people are still demanding to know why a building that was meant to be secure was so vulnerable to attack.

The hospital is heavily guarded and the government says the attackers got inside after exploding a car bomb at the gate.

But other reports suggest some attackers were already inside the hospital when the violence began, meaning militants had infiltrated the high-security site.

There is also a lack of clarity over how many people died. Some hospital workers quoted in local media said the toll was much higher than the figure of about 50 reported by the government.

The so-called Islamic State group said it carried out the attack, but some eyewitnesses later told media the assailants shouted slogans in support of the Taliban.

The deputy interior minister was sacked in the immediate aftermath of the attack.