The nonprofit group, which works in challenging areas around the world, blamed the Saudi-led coalition that's bombing Yemen for carrying out the attack -- an allegation the Gulf kingdom denied.
One staff member was lightly injured as those inside the building, including two patients, fled the assault, said Doctors Without Borders, which is also known as Medecins Sans Frontieres, or MSF.
The bombing comes in the wake of another airstrike that hit a MSF hospital in Kunduz, Afghanistan, on October 3. The United States said it had mistakenly struck the facility. President Barack Obama apologized to Doctors Without Borders
, but the group has demanded an independent commission investigate what it has said was a war crime.
The Kunduz attack killed at least 30 people, the organization reported this past weekend
, a toll that increased from earlier reports. One additional staff member was recently confirmed to have died, the group said, bringing the total number of medical staff killed to 13. Ten patients, including at least three children, died. Seven other bodies were found in the wreckage but could not be identified, though the organization presumes them to be another staffer and two patients.
At the time, Kunduz had seen a resurgence of the Taliban
and the U.S. was assisting Afghan forces in fighting.
The clinic in Yemen, where a civil war is raging
, is in the northwestern town of Haydan, according to Doctors Without Borders.
The facility, which serves a population of 200,000, was the only life-saving clinic in the region, said Dalila Mahdawi, a spokeswoman for the group. It handled 150 emergency cases each week. It had treated 3,400 injured people since May, staff said.
"This attack is another illustration of a complete disregard for civilians in Yemen, where bombings have become a daily routine," said Hassan Boucenine, Doctors Without Borders' head of mission in Yemen.
Earlier this year, the Saudi-led coalition began the campaign of airstrikes in an effort to curb the advance of Houthi rebels who had driven the government of President Abdu Rabu Mansour Hadi out of the capital.
The Saudi-led coalition denies conducting airstrikes in the vicinity of the Doctors Without Borders clinic, according to the coalition spokesman Ahmed Asseri. "Our operations were along the Saudi border, not inside the city," Asseri told CNN.
Two senior Yemen Health Ministry officials confirmed the airstrikes on the Haydan clinic. One told CNN that most of the victims treated there were ordinary civilians and that the facility treats very few families or relatives of Houthi loyalists.
Amnesty International condemned the hit on the clinic and called for an immediate, independent investigation. The rights group said that its sources in Yemen report to them that the airstrike was from the Saudi-led coalition.
"The attack on Haydan Hospital appears to have been an unlawful attack causing harm to civilians and civilian objects. The consecutive airstrikes show deliberate targeting of the medical facility -- this is another sad day for civilians," said Philip Luther, Amnesty's director for the Middle East and North Africa. "Hospitals and medical units must be respected and protected in all circumstances - they only lose their protection against attack if they are used for military purposes - and the destruction of this one means the loss of vital humanitarian treatment for civilians across four directorates of northern Yemen."
Amnesty International suggested that the strike on the hospital, if it was deliberate, could amount to a war crime.
A clinic destroyed
Doctors Without Borders regional project coordinator Miriam Czech was not present during the airstrike, but she visited the facility in the morning and said she could still see and smell smoke. She said there are devices on the ground that appear to have not exploded, but added that she has not been able enter the facility which she described as "99% destroyed."
The emergency room, outpatient area and inpatient department, the lab and maternity area and an operating area were devastated, she said.
The first airstrike hit a side of the facility, giving the staff and two patients the chance to escape ahead of subsequent airstrikes, according to Mahdawi.
Yemeni Health Ministry employee Ali Askar was at the facility when it was hit and said he was slightly injured while escaping. He said that the only departments left standing are the X-ray room and the medical staff room, but the windows and walls were destroyed.