The attack occurred on 15 August 2016 and eventuates in the decision by MSF to withdraw from four other hospitals in the region because of the dangers of Saudi airstrikes.
They also claimed to have been targeted by Houthi forces without go if specific examples.
The report also described an attack on a clinic in Taiz in early December, 2015, AMN reports.
The MSF report said: "While there are significant differences in the circumstances surrounding each incident, in both cases, the bombings hit fully functioning health facilities and the protected nature of the medical mission was not respected.
"The internal investigations of the Abs and Taiz incidents also conclude that the neutrality and impartiality of the facilities had not been compromised before the attacks and therefore there was no legitimate reason to attack them."
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