ISTANBUL — After Iran launched a retaliatory wave of missiles and drones toward Israel, a rare direct attack by Tehran, much of the Middle East found itself in uncharted territory: bracing for further violence while scrambling to interpret the new rules of confrontation between the region’s most powerful adversaries.

Iranian-backed militant groups that have participated in attacks on Israel over the last six months — in Yemen, Lebanon and Iraq — congratulated Iran for the barrage but indicated that, this time, they had largely stayed out of the fray.

Arab governments, already struggling to contain popular fury at Israel’s deadly military offensive in Gaza, pleaded for calm.

By late Sunday, the question of whether there would be further regional escalation had shifted to Israel, which said it was weighing its response. But Iran’s apparent efforts to stave off Israeli retaliation — by giving advance warning of its attacks, and making minimal use of its proxies — were no guarantee that a broader war would be avoided, analysts said.

Despite Iran’s attempt to limit the fallout, “I don’t think you can control how escalation happens,” said H.A. Hellyer, an expert on the Middle East and security studies at the Carnegie Endowment for International Peace and the Royal United Services Institute in London.

“These things always run the risk of spinning out of control.”

Saudi Arabia said it was deeply concerned and called for the “highest levels of self-restraint,” according to a foreign ministry statement Sunday. The United Arab Emirates warned of growing “instability.”

Egypt declared a state of “maximum alert,” local media reported. A foreign ministry statement emphasized the need for “maximum self-control to prevent further instability and tension in the region.”

Of all the Arab states, Jordan appeared to be the most vulnerable after Sunday’s attack because of its decision to shoot down some of the Iranian projectiles: a favor to Israel that may leave the monarchy facing even greater anger from a public already seething over the war in Gaza. The country, which has a peace treaty with Israel, as well as a large population of Palestinian descent, has seen regular protests against Israel since the war in Gaza began — and they have intensified in recent weeks.

Jordan’s role on Saturday earned derision on social media — with one picture showing King Abdullah II in an Israeli uniform. The Jordanian government, in a statement, said the munitions were shot to down to prevent them “from endangering the safety of our citizens and residential and populated areas.”

That move certainly “created pressure on Jordan, and already there are accusations” it was protecting Israel, said Saud al-Sharafat, a former brigadier general in the Jordanian General Intelligence Directorate and founder of the Sharafat ِCenter for the Study of Globalization and Terrorism.

The Iranian strikes also caused panic in Jordan, he said. “Iran wanted to send several messages: the primary is responding to Israel in its backyard, and another message is embarrassing Jordan politically and popularly.”

Iran’s attack on Israel early Sunday appeared “incredibly telegraphed and choreographed,” based on the use of drones that took hours to arrive, giving Israel and allies plenty of time to prepare and shoot them down in transit, Hellyer said. No one was killed in the assault, though a young girl was injured in a Bedouin town in the south.

The barrage was the result of an escalatory cycle that Israel set in motion on April 1, with strikes on an Iranian diplomatic facility in Syria that killed two senior commanders in its Islamic Revolutionary Guard Corps, he said.

Before the attack, “the Iranians have made it very clear over the past six months that despite all the bravado and the rhetoric and basically the chest thumping, they don’t want to enter into a regional conflict,” Hellyer said. After its commanders were killed, Iran and its allies suggested Tehran would respond directly — altering what is often described as a shadow war between Iran and Israel, because the conflict largely occurs in third countries or through proxies.

The point of Sunday’s attack seemed to be “to show their bona fides as the resistance leader” and advance Iran’s reputation in the Arab world and beyond, Hellyer said.

John Kirby, the spokesman for the National Security Council, said during an appearance on CNN’s “State of the Union” on Sunday that while some of the attacks on Israel had come from proxies, the “vast majority of weapons that were fired at Israel came from Iran proper.”

During the Gaza war, Iran’s allies have shown both a willingness to carry out attacks against Israel or U.S. military targets and a sensitivity to domestic concerns, when their actions have threatened more destabilizing consequences.

Hezbollah, the Iran-backed Lebanese militant group and political party, has engaged in tit-for-tat fire along the border with Israel while seeming wary of dragging Lebanon into all-out war. In a statement Sunday, Hezbollah congratulated Iran for its “unprecedented attack targeting the unjust and aggressor enemy entity.”

The statement also tried to convey a sense that Iran had carefully calibrated its attacks, with “high appreciation of the situation of the entire region and even worldwide,” it said. “The operation achieved its precisely defined military objectives.”

In Iraq, several people close to Iranian-backed militia groups said the militias had not joined the Iranian attack, partly out of consideration for Iraq’s prime minister, who is visiting Washington.

“This military response was purely Iranian, without any participation or assistance from anyone,” Mahdi al-Kaabi, a spokesman for the Harakat Hezbollah al-Nujaba, a militia that has claimed several attacks on U.S. forces, said in a message to The Washington Post on Sunday. But they were “ready to participate in any operations” against Israel, he added, including if it retaliated against Iran.

Officials with Yemen’s Iran-backed Houthi militia — which has carried out months of maritime attacks against commercial vessels — also sought to downplay their involvement in the overnight attack.

“We congratulate Iran for responding to the attack and support Iran’s legitimate right to defend itself,” Nasraddin Amer, chairman of the Sanaa-based Saba News Agency, the official Houthi news platform, told The Post. “We have been involved in the war against Israel since the beginning of the aggression, and our operations have been almost daily.”

“If we had participated, we would have no embarrassment in announcing it,” he said.

Dadouch reported from Beirut, Parker from Cairo and Salim from Baghdad. Heba Farouk Mahfouz in Cairo and Ali Al-Mujahed in Sanaa, Yemen, contributed to this report.

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