The Iranian-aligned Houthis said they struck two Saudi oil tankers as part of a naval blockade on Saudi Arabia on Thursday, threatening to create a second chokepoint on global oil supplies alongside Iran’s near-closure of the Strait of Hormuz.

Meanwhile, the US military said it launched a new round of strikes on Iran at President Donald Trump’s direction on Wednesday, marking a 12th successive night of American attacks.

The Yemen-based militants, who control areas near the Bab el-Mandeb Strait on the opposite end of the Arabian Peninsula from the Strait of Hormuz, said on Monday they were imposing a naval blockade on Saudi Arabia in what some analysts have viewed as a tactical move by Iran to seek leverage.

Even before the renewed threats to shipping traffic in the Red Sea, Iran’s near-total blockade of the Strait of Hormuz had stoked inflation around the world, pushing up oil prices and squeezing US gasoline consumers at a time when the unpopular war has put Trump’s Republican allies under pressure ahead of congressional elections in November.

Five tankers changed course in the Red Sea to avoid the Bab el-Mandeb Strait on Wednesday, and three tankers loaded with Saudi oil for China and India made U-turns on Tuesday.

The Houthis said their forces carried out missile and drone strikes on two Saudi oil tankers in the Red Sea, identifying them as the Encelia and the Layla.

Saudi state news agency SPA cited an official source as saying the Encelia was struck, causing a fire at the bow. The attack on the Layla remained unconfirmed.

A maritime security source said Encelia had transmitted a distress call, reporting it had been struck by a missile near the Saudi port of Jizan in the Red Sea late on Wednesday. Millions of barrels per day of Saudi oil have been heading to the kingdom’s Red Sea port of Yanbu to avoid the Strait of Hormuz. If shipments cannot pass through the Red Sea’s southern strait, they have only the northern route through the Suez Canal, adding weeks and costs to the journey.

The Houthi threat to impose a naval blockade against Saudi Arabia could significantly widen the war and strain the US military, current and former US officials said.

Two Chinese very large crude carriers carrying a combined 4 million barrels of Saudi Arabian oil were heading toward the Bab el-Mandeb Strait on Thursday, shipping data showed.

Trump threatens infrastructure, Iran vows response

Before the Red Sea flare-up, Trump vowed on Wednesday to destroy an Iranian bridge or power plant every time Iran shoots at a ship in the Strait of Hormuz.

Iran’s joint military command in turn warned that if Trump’s threat against infrastructure was carried out, Iranian forces would target regional oil, gas, electricity and economic infrastructure and prevent the export of “even a single drop of oil,” Iranian state media reported.

Hours later, Iran’s Revolutionary Guards reported an explosion in what it called a mined route south of the Strait of Hormuz, saying one of three oil tankers had caught fire while the other two turned back. The Guards said the strait was under their control and “completely closed,” warning that no tanker would be allowed to enter or leave without coordination with Iran.

In 12 straight days of attacks since a June ceasefire fell apart, American strikes have widened from the south to western and central areas of Iran. The US military’s Central Command said it would continue to “further degrade” Iran’s ability to threaten ship traffic.

Iranian media reports said the US attacked a military target in Bushehr twice on Thursday, near the country’s only operating commercial nuclear power reactor, marking three strikes there in two days.

State TV reported two people were killed and 11 wounded in what a Khuzestan provincial official described as a US missile attack on the Shalamcheh border crossing with Iraq.

Despite claims from Washington that it has destroyed Iran militarily, Tehran has demonstrated it retains missile and drone capabilities.

Iran pounded vital water desalination and energy plants in Kuwait this week and struck US military assets there, in Bahrain and in Jordan.

Both Iranians and US service members killed, injured in the war

Each side has also reported an escalating human toll.

An Iranian health ministry official said 53 civilians had been killed and 592 wounded since late last month. Since the US and Israel launched the war on February 28, thousands of people have been killed and millions displaced.

The US military has said it never targets civilians, which could violate the 1949 Geneva Conventions on humanitarian conduct in war. Trump, however, has repeatedly threatened to attack civilian infrastructure, which may be targeted if it is also being used for military purposes, provided the civilian harm is not excessive.

The war has also led to the deaths of 18 US service members and injured more than 450 troops. Trump attended a ceremony on Wednesday at Dover Air Force Base in Delaware for four US service members killed in Iranian attacks on military bases over the last few days – three in Jordan and one in Iraq.

“For me it’s one of the hardest things to do as a president. But it has to be done,” Trump said before leaving for the ceremony.

Later, at a speech in Georgia, Trump struck a different tone, saying of the war, “I call it a skirmish.”