A Yemeni man peers through the gate of a building destroyed by airstrikes in Sanaa on January 5, 2016. (Photo by Yahya Arhab/EPA)

For the third time in as many months, a Doctors Without Borders hospital in Yemen has been bombed, and this time at least four people are dead and 10 injured.

The international medical humanitarian organization, also known as Médecins Sans Frontières (MSF), said in a statement that three staff members were injured — two critically — when a clinic in the Razeh district of northern Yemen was "hit by a projectile" on Sunday morning. MSF said the number of casualties "could rise, as there could still be people trapped in the rubble."

Yemen's conflict escalated in late March when a Saudi-led coalition began targeting Houthi rebels and their allies loyal to former Yemeni president Ali Abdullah Saleh. The UN has confirmed at least 2,795 civilian deaths in Yemen since March. A majority of the deaths have reportedly been by coalition airstrikes.

MSF could not confirm who was behind the attack on Sunday, but said planes were seen flying over the facility at the time. MSF's hospital in the city of Hayden was destroyed by Saudi airstrikes on October 27, and nine people were wounded when coalition bombs hit a health center in the city of Taiz on December 3. The Saudis initially admitted carrying out the October airstrikes, calling the attack a "mistake" and promising to investigate, then reversed course and denied responsibility.

MSF says it informs all parties, including the Saudi coalition, of the exact GPS coordinates of its medical facilities.

"We are in constant dialogue with them to ensure that they understand the severity of the humanitarian consequences of the conflict and the need to respect the provision of medical services," MSF director of operations Raquel Ayora said.

The International Committee of the Red Cross said in November that more than 100 hospitals in Yemen have been attacked since the Saudi-led coalition began its bombing campaign in March.The hospital in Razeh, Shiara Hospital, had already been bombed once before MSF started working there in November.

"We strongly condemn this incident that confirms a worrying pattern of attacks to essential medical services and express our strongest outrage as this will leave a very fragile population without healthcare for weeks," Ayora said. "Once more it is civilians that bear the brunt of this war."

Reuters contributed to this report.

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