The self-proclaimed Islamic State has claimed responsibility.
Gunmen dressed as medics stormed a hospital in the Afghan capital, Kabul, battling security forces for hours.
Most of those killed were patients in their beds.
Landing on the roof, Afghan special forces eventually killed the attackers - but not before the militants killed more than 30 people and wound dozens more.
Survivor Mohammad Arif describes the terror.
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"I don't know exactly what happened, we were inside the room. When we were rescued by Special Forces there were dead people including patients and doctors."
In a statement IS claimed responsibility for the attack.
IS is opposed to both the Western-backed government in Kabul and the Taliban.
Christopher Kolenda from the Centre for Global Policy in the U-S says, with I-S now losing ground in Iraq and Syria - fighters will inevitably end up in Afghanistan.
"Now that ISIS is on the road to defeat at in Iraq and Syria you have to ask yourself where are they going to go? Where are these fighters these terrorists going to go? And unfortunately Afghanistan as long as it remains unstable like this is highly attractive to groups like ISIS for relocation."
Since IS announced its presence in Afghanistan around two years ago - it's mainly engaged with Afghan forces and Taliban fighters in the east of the country near the Pakistan border.
The Afghan Government claims to have rooted out IS in the east - but it's still prolific in mountainous areas they control.
Hamid Saboory a political analyst with Kabul think tank Afghanistan Analysis and Awareness.
"I think they are able to do more but I think they are not doing enough that is why we witness incidents of such kind. Which at the end inflicts heavy causalities to our civilians as well as our national security forces."
