A spate of tit-for-tat attacks between Saudi Arabia and Houthi rebels in Yemen is escalating, threatening to break a fragile truce that has held for four years.

Houthi supporters protesting an attack on the San’a airport in Yemen.

A return to all-out war between the Saudis and the Iran-backed militant group would heap more pressure on global energy markets already strained by the U.S.-Israeli war on Iran and Tehran’s retaliatory chokehold on the Strait of Hormuz. It could also bring catastrophic consequences to the people of Yemen, where deadly famine took hold when the country’s civil war was at its peak.

So far, Riyadh has calibrated its responses as the Houthis test their limits, but experts on the conflict say they see little room for de-escalation. The militants are under growing economic pressure, which they blame on a Saudi-enforced blockade of Yemeni ports and airspace.

Meanwhile, Iran is taking advantage of the situation to inflict pain on the kingdom without attacking it directly.

“Iran is fanning the flames of this conflict—that’s without question—but the Houthis tend to do things when it makes sense for them,” said Allison Minor, a former U.S. official on Middle East policy now at the Atlantic Council think tank. “I think we’re very close to a resumption of all-out war. I’m not seeing an off-ramp right now.”

Tensions peaked on Saturday when the Royal Saudi Air Force struck military targets in Yemen’s coastal province of Hodeida, according to a Saudi-led coalition opposing the Houthis. The Houthis responded with drone and missile attacks on facilities of Aramco, Saudi Arabia’s state-owned energy firm, in the cities of Jizan and Yanbu, the main spigot for oil exports off the country’s western coast. Saudi Arabia didn’t disclose whether the facilities suffered any damage.

Hours later, Houthi launch sites and weapons depots were targeted in several locations, including Marib and Al-Jawf, according to a Yemeni broadcaster run by the Saudi-backed government in Aden. These were among the coalition’s first airstrikes inside Yemen since a United Nations-brokered truce took effect in 2022, intensifying conflict on its volatile front lines.

On Sunday, the Houthis claimed they shot down a Turkish surveillance drone operated by the Saudis. Saudi Arabia’s foreign ministry didn’t immediately reply to a request for comment.

“For now, I think it’s still a tit-for-tat and there’s hope that maybe this can be contained,” said Umer Karim, a researcher focused on Saudi policy and Gulf geopolitics at the University of Birmingham in the U.K. “But the way things are going, I don’t think so.”

Saudi Arabia intervened against the Houthis a decade ago after the group seized a swath of territory during the country’s civil war. Since then, Riyadh has backed Yemen’s internationally recognized government and led the coalition of Arab militaries that supported its fight against the militants.

The civil war in Yemen lasted seven devastating years. The truce reached in 2022 was meant to ultimately ease restrictions on fuel imports and flights. Riyadh’s diplomatic rapprochement with Iran, the Houthis’ sponsor, the following year helped maintain a tenuous peace even though little progress was made politically.

“Now we are seeing a completely different story: The Iranians are pushing the Houthis to escalate,” said Ahmed Nagi, senior Yemen analyst for the International Crisis Group.

Until recently, the Houthis had largely sat out the war that began in late February when the U.S. and Israel attacked Iran. That changed in early July, when the militants tried to test the Saudi air blockade with a direct flight from Tehran that landed in the rebel-controlled capital, San’a.

About a week later, the Houthis accused Riyadh of bombing the runway, forcing them to divert another flight from Iran, which the coalition prohibits over fears they could be used to transport weapons and military advisers. Yemen’s Saudi-backed government claimed responsibility for the strike.

The San’a airport strike set off an escalatory spiral. The Houthis fired ballistic missiles and drones at a civilian airport in southwestern Saudi Arabia, Riyadh said. A week later, the Houthis announced a blockade on Saudi oil shipments through the Red Sea, threatening to cut off a vital lifeline for global energy supplies.

Since the war between the U.S. and Iran began, Tehran and Riyadh have sought to limit direct confrontation. Even as Iran tightened its grip on Hormuz, Saudi Arabia was able to cushion the blow—to itself and the global economy—by rerouting some 4 million barrels of oil a day to the Red Sea.

Now that exit is under threat by the Houthis, whose territory along Yemen’s coast overlooks the Bab al-Mandeb shipping lane, a narrow strait that connects the southern Red Sea to, ultimately, markets in Asia and elsewhere. Last week, the price of oil soared past $100 a barrel when the Houthis struck two Saudi tankers. A third was hit on Friday, setting off this weekend’s escalation.

With Iran’s support and a cause that pleases its domestic base—trying to break the Saudi-led blockade—the Houthis are unlikely to back down, said Farea al-Muslimi, a research fellow at the Chatham House think tank.

“The Houthis always have one solution for everything, which is to find an enemy, blame them, and go to war,” he said.

Write to Feliz Solomon at feliz.solomon@wsj.com