TEHRAN, Iran >> 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 all crude oil traded worldwide passes.

The area around the strait in the past has 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.”

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, both 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 to global prices.