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At least 11 people were killed and 19 injured Monday after airstrikes hit a hospital in northern Yemen that Doctors Without Borders was helping operate, the group said.

The international aid organization — also known as Médecins Sans Frontières, or MSF — said Abs Hospital in the northern Hajjeh province was hit by the strikes at 3:45 p.m. local time.

Destruction at the hospital in Abs district in the northern province of Hajja, Yemen on Aug. 15. Reuters

The explosion immediately killed nine people, including a Yemeni staff member, the group said in a statement. Two more people died while being transported to another local hospital.

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The conflict in Yemen pits the internationally-recognized government backed by a Saudi-led coalition against Shiite rebels known as Houthis, who captured the capital nearly two years ago.

.@MSF: Medical teams still attending wounded after the airstrike that took place today at 15:45 in #Abs #Saada #Yemen — أطباء بلا حدود-اليمن (@msf_yemen) August 15, 2016

In the statement, the group said that the hospital's GPS coordinates were repeatedly shared with all sides of the conflict. Despite a recent United Nations resolution calling for an end to such attacks, the statement added, Monday's airstrikes marked the fourth time an MSF facility had been targeted in less than a year.

On Saturday, at least 10 Yemeni children were killed and dozens more were injured after a school was hit by air strikes, the Associated Press reported.

On Monday, the official Saudi Press Agency said that it had "seen the UN Secretary General’s call for an investigation into the recent claim by Medecins Sans Frontiers (MSF) that Coalition airstrikes have hit a school in Yemen causing casualties among the children."

Related: Doctors Without Borders: Airstrike on Aleppo, Syria, Hospital Kills 14

Independent investigators following international standards will examine the incident, the statement added.

Several humanitarian groups condemned the attack on Monday. In a joint statement, Oxfam, Save the Children and others pointed out that air strikes were behind more than half of the 785 children killed and 1,168 wounded in Yemen last year.

Between April and August of 2016, the statement said, 272 civilians have been killed there and 543 were injured.