China, Iran and Russia conducted joint naval drills Tuesday in the Middle East, offering a show of force in a region still uneasy over Tehran's rapidly expanding nuclear program and as Yemen's Houthi rebels threaten new attacks on ships.

The joint drills, called the Maritime Security Belt 2025, took place in the Gulf of Oman near the strategic Strait of Hormuz, the narrow mouth of the Persian Gulf through which a fifth of the world’s crude oil passes. The area around the strait has in the past seen Iran seize commercial ships and launch suspected attacks in the time since President Donald Trump first unilaterally withdrew America from Tehran's nuclear deal with world powers.

The drill marked the fifth year the three countries took part in the drills.

This year's drill likely sparked a warning late Monday from the British military's United Kingdom Maritime Trade Operations center, which said there was GPS interference in the strait, with disruptions lasting for several hours and forcing crews to rely on backup navigation methods.

"This was likely GPS jamming to reduce the targeting capability of drones and missiles," wrote Shaun Robertson, an intelligence analyst at the EOS Risk Group. "However, electronic navigation system interference has been reported in this region previously during periods of increased tension and military exercises."

US-patrolled waters

Russia's Defense Ministry identified the vessels it sent to the drill as the corvettes Rezky and the Hero of the Russian Federation Aldar Tsydenzhapov, as well as the tanker Pechenega. China's Defense Ministry said it sent the guided-missile destroyer Baotou and the comprehensive supply ship Gaoyouhu. Neither offered a count of the personnel involved.

Neither China nor Russia actively patrol the wider Middle East, whose waterways remain crucial for global energy supplies. Instead, they broadly cede that to Western nations largely led by the U.S. Navy's Bahrain-based 5th Fleet. Observers for the drill included Azerbaijan, Iraq, Kazakhstan, Oman, Pakistan, Qatar, South Africa, Sri Lanka and the United Arab Emirates — with the Americans likely keeping watch as well.

However, China and Russia have deep interests in Iran. For China, it has continued to purchase Iranian crude oil despite facing Western sanctions, likely at a discount compared with global prices. Beijing also remains one of the top markets for Iranian imports.

Russia, meanwhile, has relied on Iran for the supply of bomb-carrying drones it uses in its war on Ukraine.

Iran highlights drills

The drills marked a major moment for Iran's state-run television network. It has aired segments showing live fire during a night drill and sailors manning deck guns on a vessel. The exercises come after an Iranian monthslong drill that followed a direct Israeli attack on the country, targeting its air defenses and sites associated with its ballistic missile program.

While Tehran sought to downplay the assault, it shook the wider populace and came as a campaign of Israeli assassinations and attacks have decimated Iran's self-described "Axis of Resistance" — a series of militant groups allied with the Islamic Republic. Syrian President Bashar al-Assad was also overthrown in December, further weakening Iran's grip on the wider region.

All the while, Iran has increasingly stockpiled more uranium enriched at near-weapons-grade levels, something done only by atomic-armed nations. Tehran has long maintained its program is for peaceful purposes, even as its officials increasingly threaten to pursue the bomb.

Iran's nuclear program has drawn warnings from Israel and the U.S., signaling that military action against the program could happen. But just last week, Trump sent a letter to Iranian Supreme Leader Ali Khamenei seeking a new nuclear deal. Iran says it hasn't received any letter but still issued a flurry of pronouncements over it.

Houthis renew threats

As a shaky ceasefire holds in Israel's war against Hamas in the Gaza Strip, Yemen's Houthi rebels said they were resuming attacks on shipping in the Red Sea and the Gulf of Aden, as well as the Bab el-Mandeb Strait that connects the two waterways.

The rebels' secretive leader, Abdul-Malik al-Houthi, warned Friday that attacks against Israel-linked vessels would resume within four days if Israel didn't let aid into Gaza. As the deadline passed Tuesday, the Houthis said they were again banning Israeli vessels from the waters off Yemen.

Although no attacks were reported, it has put shippers on edge. The rebels targeted over 100 merchant vessels with missiles and drones, sinking two vessels and killing four sailors, since November 2023.