The charity Medecins Sans Frontieres (MSF) says it will withdraw staff from six hospitals in north Yemen after a Saudi-coalition air strike hit one of its buildings, killing 19 people.
Monday's attack was the fourth and deadliest on MSF's facilities in Yemen.
The French charity said in a statement it was "unsafe for both patients and staff" in the Saada and Hajjah governorates to continue.
They said hospitals will remain staffed by local volunteers.
MSF said air strikes have continued even though they have shared the satellite co-ordinates of their hospitals with the parties involved in the conflict.
"Coalition officials repeatedly state that they honour international humanitarian law, yet this attack shows a failure to control the use of force and to avoid attacks on hospitals full of patients."
"MSF is neither satisfied nor reassured by the SLC's [Saudi-led coalition] statement that this attack was a mistake.
"The decision to evacuate the staff from a project is never taken lightly but in the absence of credible assurances that parties will respect the protected status of medical facilities there may be no other option."
The area hit is a stronghold of the Houthi rebels who took over parts of the country in September 2014, including the capital Sanaa, and forced the government into exile.
A Saudi-led coalition force has been carrying out air strikes in Yemen since March 2015 in attempts to oust the rebels and defend the internationally recognised government of President Abedrabbo Mansour Hadi.
MSF provides emergency aid to vulnerable people in conflict zones around the world, including supporting hospitals in Syria. An air strike on an MSF-backed hospital in Aleppo in April is believed to have killed 50 people.
In December 2015, a US air strike on an MSF clinic in Kuduz, Afghanistan killed 42 people. Pentagon officials said the strike was a "direct result of human error".