Saudi Arabia Bombs Yemeni Port City Over Weapons Shipment from the U.A.E.

In the latest strike, Saudi military spokesman Maj. Gen. Turki al-Maliki said weapons and combat vehicles were targeted in the city of Mukalla, Yemen’s largest port on the Arabian Sea and the gateway to Yemen’s oil country. The weapons and vehicles were unloaded from two ships that had left the Emirati port of Fujairah and had disabled their tracking systems, Saudi officials said.

Saudi officials said the weapons were intended to support the Southern Transitional Council, a group that favors forming a separate state from northwest Yemen, which has been held by the Iran-backed Houthis since 2014. The group has won territory in recent weeks giving it control of areas along the Saudi border with Yemen.

The Saudis support a unified Yemen, though in reality, with the Houthis firmly in control of the northwest and the country’s historic capital, Sa’na, Riyadh has focused more on managing the internal conflicts between Yemeni factions and putting its own proxy forces in control of border areas.

Emirati officials and the Southern Transitional Council couldn’t be reached for comment.

The Saudis and the Emiratis are now at odds on multiple fronts in the region, clashing over the direction of the decade-old Yemen civil war and backing different factions in Sudan’s conflict. The two countries are longtime allies with each other and security partners for the U.S., but tensions have long simmered below the surface.

U.A.E. President Sheikh Mohamed bin Zayed Al Nahyan was once a mentor to Saudi Crown Prince Mohammed bin Salman, but the two leaders have feuded in recent years over who calls the shots in the Middle East.

The escalation in proxy fighting in Yemen as well as in Sudan, and the resulting tension between Saudi Arabia and the U.A.E., risks creating headaches for the Trump administration, which has invested heavily in relations with the Gulf powers. President Trump conducted a high-profile trip through the Gulf in the spring and welcomed Saudi Crown Prince Mohammed bin Salman to the White House last month.

The Southern Transitional Council now controls most of the south, having outflanked Saudi-backed forces. The south itself is at odds with the Iran-backed Houthi militia, which controls most of northwestern Yemen, including the capital, San’a.

Saudi Arabia on Thursday criticized the STC for not coordinating its military moves with other constituencies in the south.

“These movements resulted in an unjustified escalation that harmed the interests of the Yemeni people,” the kingdom said.

Saudi Arabia’s airstrikes last Friday came a day after Riyadh told the southern council to pull its forces out of Hadramout governorate, which borders the kingdom. The council assessed that the strikes were meant as a warning to withdraw or face further military action.

Write to Michael Amon at michael.amon@wsj.com