The U.N. Security Council came under sharp criticism Wednesday for its failure to implement a resolution aimed at protecting medical facilities and staff in conflict zones from Syria to Yemen and Afghanistan.

The U.N.'s most powerful body held a meeting on health care in armed conflict that by coincidence began just hours after two hospitals on rebel-held Aleppo were bombed, highlighting the lack of action to protect them.

Joanne Liu, president of Doctors Without Borders, known by its French initials MSF, blamed the failure on "a lack of political will — among member states fighting in coalitions, and those who enable them." She told the council that the failure is evident in hospital attacks since the resolution's adoption in May which have left civilians in war with "less, if any, access to life-saving medical care."

"Many attacks ... are brushed off as mistakes," Liu said. "We reject the word 'mistake'. We denounce the deliberate and systemic failure of states to avoid attacking hospitals and to appropriately control their conduct of hostilities."

In both Syria and Yemen, four of the five veto-wielding permanent members of the Security Council "are implicated in some way in these attacks," she said, a reference to Russia, the United States, Britain and France.

Liu cited the destruction of an MSG hospital in Abs, Yemen in early August carried out by the Saudi-led coalition which killed 19 people, the fourth such attack on an MSF facility in the country. A week later, an MSF-supported hospital in Idlib, Syria was destroyed in repeated air strikes, killing four hospital staff and nine patients and cutting life-saving care to 70,000 people.

U.N. Secretary-General Ban Ki-moon implicitly accused Syria and close ally Russia of committing war crimes in the besieged Syrian city of Aleppo in Wednesday's hospital attacks. He said what was happening in the city, the target of a Syrian government offensive backed by Russia, is worse than "a slaughterhouse."

"Let us be clear: Those using ever more destructive weapons know exactly what they are doing. They know they are committing war crimes," he said.

Ban also urged international action and accountability, stressing that since May "there has been no let-up." In addition to attacks on health care facilities in Syria and Yemen, he cited a suicide attack on Pakistan's Sandeman Provincial Hospital in August that killed more than 70 people.

The U.N. chief urged the Security Council to take "decisive steps" to protect health facilities and medical staff. These include ensuring that laws and weapon sales respect the provision of medical care in conflict, that parties to conflict take precautions to protect medical staff and facilities, that those responsible for violating international law are prosecuted and punished — and that people and communities affected by attacks receive reparations.

Russia's deputy U.N. ambassador Evgeny Zagaynov told the council that Syria and Russia are being blamed for "the majority of strikes on civilian facilities in Syria" — including Wednesday's hospital bombings in Aleppo — without any independent investigation and verification.

He said similar unacceptable incidents have resulted from "the destabilizing policy carried out by the U.S. and its allies." He cited last October's U.S. military attack on a Doctors Without Borders trauma hospital in the Afghan city of Kunduz which killed 14 staff and 28 patients and caretakers, noting that while the U.S. took responsibility, those responsible are still at work.

Zagaynov called for an end to "anti-Russian demagoguery" and a united international effort to end the Syrian conflict as soon as possible. He said "a very good basis" is Russian-American cooperation.

U.S. deputy ambassador Michele Sison said the U.S. has taken steps since Kunduz "to minimize the likelihood of future incidents."