It was late at night when a missile fired from the air slammed into the operating room at a small district hospital in Yemen’s northern Sadah province.

Hospital staff members said they had just finished tending to the last patients in the emergency room and were settling down to a dinner of bean stew and rice.

“We suddenly heard planes above us, and then everything was shaking, and there was dust everywhere,” said Yahya Quafi, a laboratory technician reached by phone in the provincial capital, also called Sadah.

They evacuated with moments to spare, taking cover in a ditch as the plane circled back for a second run at the building.

The attack on Oct. 26, which staffers blame on a Saudi-led coalition and which leveled the only functioning hospital for a population of 200,000, came just three weeks after a deadly U.S. strike on a trauma center in Afghanistan. In the same month, the medical group Doctors Without Borders reported that at least 12 hospitals were bombed in Syria and another in South Sudan was ransacked by tribal fighters who made off with vehicles, communications equipment and medical supplies.

Humanitarian officials worry that such attacks are shredding the international laws that give protected status to hospitals in war zones, safeguards they rely on to provide lifesaving care in some of the world’s most dangerous places.

“As awful as war is, it still has rules,” said Jason Cone, executive director of Doctors Without Borders in the U.S., as staff members gathered in New York and other cities this week in memory of the 30 people killed in the northern Afghan city of Kunduz, including at least 13 colleagues and 10 patients.

“We knowingly take the risks associated with working in war zones. But what happened in Kunduz — the precise targeting and prolonged destruction of a fully functioning hospital full of patients and health workers — transcended even the bounds of war.”

President Barack Obama has apologized for the attack, which Army Gen. John F. Campbell, the top U.S. commander in Afghanistan, said was a mistake. The U.S. military, NATO and the Afghan government are investigating. But Cone suspects that these inquiries will be incomplete because they are likely to focus on whether the American military’s rules of engagement were followed, not whether those rules meet international standards.

His organization is calling for a separate investigation by the International Humanitarian Fact-Finding Commission, a body set up under the Geneva Convention. But that would require the assent of the U.S. and Afghanistan, which has not been provided.

“It’s important because it’s looking at what happened through the lens of humanitarian law,” Cone said. “These are the basic protections that our teams need to be able to operate worldwide, not just in Afghanistan. We need to make sure that those laws are being adhered to.”

Humanitarian officials say attacks on hospitals, their staffs and patients have been reported in dozens of conflicts since the Geneva Convention of 1949 and related protocols prohibited combatants from targeting such structures. They have occurred in places such as the Balkans, Somalia, Rwanda and the Gaza Strip, but the frequency and visibility of the attacks appears to be increasing, said Nancy Aossey, who has led the Los Angeles-based International Medical Corps since 1986.

That is partly a function of the growing reach of medical aid groups, Aossey acknowledged. But she also cited the complexity of recent conflicts: lawless insurgencies and proxy wars in which loyalties are fluid and numerous interests have a stake.

Where once an attack on a remote medical post might have gone unnoticed, it is now recorded on cellphone video and shared instantly.

The International Committee of the Red Cross documented more than 1,200 attacks on hospitals or within their perimeters in 2013 and 2014 alone.

In Syria, health structures and their employees have repeatedly come under fire in what rights activists describe as a deliberate campaign by government forces to deny medical care in areas controlled by their opponents.

“We’ve never seen anything this extreme,” said Widney Brown, director of programs for Physicians for Human Rights.

The New York-based group says it has documented attacks on 313 health structures and the killing of 679 personnel in Syria since the uprising against President Bashar Assad began in March 2011. Government forces have been responsible for more than 90 percent of these attacks, the group says.

In recent weeks, the Russian military has also been accused of launching airstrikes on hospitals in Moscow’s new campaign on behalf of Assad’s government, charges denied by the Russian authorities.

A doctor who directs a field hospital in Sarmin, in Syria’s northwestern Idlib province, said his facility had been hit more than a dozen times. A pair of airstrikes Oct. 20 killed 12 people and injured 28.

“When I am in the hospital, I feel like I am sitting on a bomb,” the doctor said in a statement released by the Syrian American Medical Society, which operates the facility. “It is only a matter of time until it explodes.” The group did not provide the doctor’s full name.

In Yemen, at least 51 medical structures have been damaged or destroyed by airstrikes and fighting since a Saudi Arabian-led and U.S.-backed coalition launched an air campaign in March aimed at restoring ousted President Abdu Rabu Mansour to power, according to the World Health Organization. Aid workers accuse all sides of a willful disregard of the rules of law in favor of achieving their military objectives.

“We are used to that with militias,” said Hassan Boucenine, chief of mission for Doctors Without Borders in Yemen. “But I really hold nations, the United States and Saudi Arabia, to a higher standard.”

He said his organization had provided the coordinates of the hospital hit last month to the coalition and marked the roof with the group’s flag, a standard practice the group said was also followed in Kunduz.

Abdullah Moallemi, Saudi Arabia’s representative at the United Nations, confirmed that the coalition had received the coordinates and placed them on a list of forbidden targets. “Accordingly, this hospital could not have been targeted by the coalition forces,” he said in a televised address last week.

Moallemi said the coalition was not conducting operations in Sadah at the time of the strike and promised a full investigation. Hospital staff members say coalition aircraft had been carrying out strikes in their district for about an hour before the facility was hit. But they felt safe because it had never taken a direct hit before.

Those who carry out such attacks often justify their actions by accusing the protected facilities of harboring armed combatants.

Campbell, the U.S. general, said the airstrikes in Kunduz were carried out on behalf of Afghan forces under attack by Taliban fighters who had recently taken control of the city. Afghan officials have been quoted as saying that the militants had been firing rockets from inside the hospital compound.

The hospital in Kunduz, the only trauma center of its kind in northeastern Afghanistan, had treated both Taliban and Afghan army personnel, Cone said. But they were required to leave their weapons outside, and he said there was no evidence of military activity in the hospital.

Even if that had been the case, he said, any warring party would have been required by international law to issue a warning and allow time to evacuate the facility before launching an attack.

That didn’t happen in Kunduz, or at any of the hospitals struck last month.

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(Special correspondent Nabih Bulos contributed to the report from Athens, Greece.)