Doctors Without Borders (MSF) on Thursday said it was evacuating its staff from six hospitals in northern Yemen after 19 people were killed in an air strike on one of its facilities earlier this week.

Monday's attack on the hospital at Abs was the fourth and deadliest yet on an MSF facility in Yemen.

The decision to withdraw "is never taken lightly", the charity said in a statement.

But "given the intensity of the current offensive and our loss of confidence in the SLC's (Saudi-led coalition's) ability to prevent such fatal attacks, MSF considers the hospitals in Saada and Hajjah governorates unsafe for both patients and staff," it added.