DUBAI/SANAA (Reuters) - At least 50 soldiers from the United Arab Emirates and Bahrain were killed in Yemen on Friday in the deadliest attack on Gulf Arab troops in the Saudi-led military campaign against Houthi forces, Gulf news agencies said.

The incident took place in the oil-producing Marib area of central Yemen near the border with Saudi Arabia, apparently when Houthis rocket fire hit a weapons store at a military camp.

UAE state news agency WAM initially reported that 22 Emirati soldiers were killed, then later said the total number had risen to 45 after 23 more soldiers died of their wounds.

"A rocket and an explosion at a weapons cache has targeted the martyrs," UAE Minister of State for Foreign Affairs Anwar Gargash said on Twitter.

Bahrain's official news agency BNA said five Bahraini soldiers were killed while on duty protecting Saudi Arabia, though it appeared to be referring to the same incident.

Houthi-run media also said Houthi fighters had fired a rocket at the camp, killing dozens of Emirati and Yemeni soldiers and destroying a number of Apache helicopters and armoured vehicles.

Marib residents told Reuters they saw fire raging at the camp and plumes of smoke.

Saudi Arabia and a coalition of other Sunni Muslim Arab states intervened in Yemen's conflict in March to restore the exiled government and drive back the Iran-allied Houthis, who seized the capital Sanaa in September last year then took over much of the country.

Militias and army units loyal to exiled President Abd-Rabbu Mansour Hadi, who has taken refuge in Saudi Arabia, have made advances toward Sanaa in the last two months.

The coalition has been supporting the anti-Houthi fighters with air strikes, military training and deliveries of tanks and heavy artillery.

The Saudi-led forces had been sending military hardware to Marib, where Hadi loyalists have been preparing for an offensive against Sanaa.

Forces from the United Arab Emirates have played a leading role in bringing about the gains made by the Hadi loyalists, including driving the Houthis out of the southern port city of Aden.

The Gulf states regard the Houthis - who belong to the Zaydi branch of Shi'ite Islam - as a proxy of their arch-rival, Shi'ite Iran, while the Houthis say they are fighting a revolution against corrupt officials beholden to the West.

Before the latest incident, at least five Emirati soldiers had been killed in Yemen since the offensive began.