Saudi Arabia on Tuesday said it bombed the port city of Mukalla in Yemen over a shipment of weapons for a separatist force there that arrived from the United Arab Emirates.

The attack signals a new escalation in tensions between the kingdom and the Southern Transitional Council, which is backed by the Emirates. It also further strains ties between Riyadh and Abu Dhabi, which had been backing competing sides in Yemen's decadelong war against the Iranian-backed Houthi rebels.

A military statement carried by the state-run Saudi Press Agency announced the strikes, which it said came after ships arrived there from Fujairah, a port city on the UAE's eastern coast.

“Given the danger and escalation posed by these weapons, which threaten security and stability, the Coalition Air Forces conducted a limited military operation this morning targeting weapons and combat vehicles unloaded from the two ships at the port of al-Mukalla,” it said.

A coalition spokesperson said two ships arriving from the UAE port of Fujairah entered Mukalla port on Saturday and Sunday without authorisation from the coalition, disabled their tracking systems and unloaded large quantities of weapons and combat vehicles "to support the (STC)."

The coalition said there were no casualties or collateral damage from the strike at Mukalla port, Saudi state media reported.

There was no immediate comment from the UAE.

Two sources told Reuters that the strike targeted the dock where the cargo of the two ships was unloaded.

The STC separatists were initially part of the Saudi-led alliance that intervened in Yemen in 2015 against the Houthis. But they subsequently decided to seek self-rule in the south.

Since 2022, they have been part of an alliance that controls southern areas outside Houthi control under a Saudi-backed power-sharing initiative.

At present, UAE-backed forces control large swathes of land in the south including the strategically important Hadramout province.

Hadramout is on the border with Saudi Arabia and they have cultural and historical ties; many prominent Saudis trace their origins to the area.

The Houthis control the northern part of the country, including the capital Sanaa, after forcing the Saudi-backed government to flee south.

"We will continue to prevent any military support from any country to any Yemeni faction without coordination with the legitimate government," the coalition added.