Saudi-led coalition aircraft attacked a Médecins Sans Frontières-supported hospital in northern Hajja province in Yemen on Monday, killing at least seven people and wounding 13.
The airstrike comes less than 48 hours after another attack on a school killed 10 children in Haydan, a region in Yemen's northwestern Saada province.
Reuters reported that a witness at the scene of Monday's attack in the Abs district said medics were not able to evacuate the wounded immediately, because they feared more attacks by warplanes that continued to fly over the area.
Médecins Sans Frontières, a humanitarian group also known as Doctors Without Borders, confirmed the airstrike on its official Twitter account, but said the number of deaths and injuries remained unclear.
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The group said it had worked with the hospital since July 2015.
Reuters reported that a spokesman for the Saudi-led coalition did not immediately respond to a request for comment on the reported attack.
In the Saturday attack, the coalition said it had targeted a Houthi training facility, not a school, and that the dead and injured children were Houthi militia recruits. The Houthis are the Shiite faction being targeted by the Saudi-led campaign.
The two attacks come just days after the US announced that it was selling $1.15 billion in weapons to Saudi Arabia.
The US State Department last month approved nearly a billion dollars in aerial weapons sales — including 14,000 Paveway guided bombs and Joint Direct Attack Munition (JDAM) kits — to the United Arab Emirates, which is also part of the coalition flying bombing missions in Yemen.
The US military also supports the Saudi-led coalition with aerial refueling and intelligence.
A spokesperson for Amnesty International said the circumstances of Monday's attack on the hospital could be a war crime, and "must be thoroughly and independently investigated."
"Today's air strike appears to be the latest in a string of unlawful attacks targeting hospitals highlighting an alarming pattern of disregard for civilian life," said Magdalena Mughrabi, Amnesty International's Deputy Director of the Middle East and North Africa Program.
The United Nations estimates that 2,800 civilians have been killed since Saudi Arabia began military operations in March 2015 to put Saudi-backed Yemeni President Abd-Rabbu Mansour Hadi back into power and to halt the gains of the Houthis.
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