A Saudi-led coalition rained down missiles in Yemen from Friday into Saturday, an intense attack that a U.N. official called a breach of international humanitarian law

A Saudi-led coalition rained down missiles in Yemen from Friday into Saturday, an intense attack that a U.N. official called a breach of international humanitarian law.

The Saudis admitted that the latest attack on Yemen -- 130 airstrikes in a 24-hour period -- included the targeting of schools and hospitals.

The hospitals and schools that were hit “functioned as weapons storage sites”, coalition spokesman Brig. Gen. Ahmed Asiri claimed in a statement, a claim Israeli officials usually repeat to justify its attack on civilians.

The operations were "targeting headquarters of the Houthi leaders," Asiri said.

“Civilians had been warned ahead of time to leave the cities of Sadaa, Maran, Albiqaa and the border area between Saudi Arabia and Yemen,” Asiri said.

That rationalization for Friday and Saturday airstrikes was rejected by Johannes Van Der Klaauw, the U.N. humanitarian coordinator for Yemen.

"The indiscriminate bombing of populated areas, with or without prior warning, is in contravention of international humanitarian law," Van Der Klaauw said in a statement.

The U.N. official said he was especially concerned about the airstrikes on Saada, "where scores of civilians were reportedly killed and thousands were forced to flee their homes after the coalition declared the entire governorate a military target."

Before the latest round of airstrikes, two Houthi officials said the coalition dropped leaflets warning that the Saudis would consider the entire governorate of Saada as an enemy military zone starting Friday night.

Doctors Without Borders (MSF), one of the international aid organizations with a presence in Saada, confirmed the heavy bombing there.

"The bombing of civilian targets, with or without warning, is a serious violation of international humanitarian law," said Llanos Ortiz, MSF medical coordinator in Yemen. "It is even more serious to target a whole province."

It is impossible for an entire population to leave within a few hours, Ortiz said. Many Saada residents lack vehicles to flee or access to phone or other communication networks, he added.

One emergency coordinator for MSF, Teresa Sancristóval, said: "Even though the city is noticeably emptier many people were not aware of the order of evacuation -- it hasn't been heard by the entire population."

At least one hospital had to restructure its layout because of the airstrikes. The hospital is running out of safe places, so locations like the maternity ward were also being used as the pediatric and inpatient departments for women, Doctors Without Borders said.