GENEVA (Reuters) - The United Nations is beefing up its inspections of ships bringing humanitarian aid to Yemen to ensure that no military items are being smuggled and to speed delivery of desperately-needed relief supplies, U.N. and Saudi officials say.

A ship unloads a cargo of wheat at the Red Sea port of Hodeida, Yemen April 1, 2018. REUTERS/Abduljabbar Zeyad

The move comes as the armed Houthi movement controlling much of northern Yemen steps up attacks on the kingdom, hitting a Saudi oil tanker on Tuesday. [nL5N1RG4DR]. A Saudi-led coalition said overnight that Riyadh’s air defence had intercepted a missile which Houthis said was aimed at storage tanks belonging to Saudi Aramco oil company. [nL5N1RH673]

Saudi Arabia accuses arch-rival Iran of supplying missiles to the Houthis, who have taken over the Yemeni capital Sanaa and other parts of the country. Tehran and the Houthis deny the allegation.

Under an arms embargo imposed by the U.N. Security Council, monitors from the U.N. Verification and Inspection Mechanism (UNVIM) are based in ports in Djibouti, Dubai, Jeddah and Salalah to observe screening of cargo destined for Yemen.

“We met with the UNVIM director and his team in Riyadh and we agreed on improved and enhanced capability,” Saudi Ambassador to Yemen Mohammed S. Al-Jabir told reporters in Geneva on Wednesday.

He said UNVIM would increase its inspectors to 10 from four and its monitors to 16 from six and would also improve its technology to inspect ships.

The team supporting the U.N. Humanitarian Coordinator in Yemen Lise Grande confirmed to Reuters on Thursday those steps taken to increase the number of monitors and inspectors and the use of scanning equipment.

A major U.N. pledging conference on Yemen was held this week, drawing pledges of more than $2 billion toward a $3 billion U.N. humanitarian appeal. [nL5N1RG2AQ]

Saudi Arabia and the United Arab Emirates, which lead coalition air strikes in Yemen in support of the internationally-recognised government of President Abd-Rabbu Mansour Hadi, have contributed $930 million.

“We are cooperating with the UNVIM and other U.N. organizations to facilitate and to increase the amount of ships that arrive to Hodeidah port,” Jabir said, referring to Yemen’s main port for humanitarian and commercial goods, under Houthi control.

UNVIM only checks commercial and aid ships going to northern ports under Houthi control - Hodeidah, Salif and Ras Isa - and not to Aden, which is under government control.

Yemen, the Arabian peninsula’s poorest country, is reeling from the world’s worst humanitarian crisis where 22 million people need vital assistance.

When the Houthis fired missiles at Riyadh last November, the Western-backed coalition shut Yemen’s airports and ports. The United Nations said that blockade raised the danger of mass starvation and it was partially lifted.

But diplomats say Saudi Arabia has been under heavy pressure from its main ally the United States to speed up aid.

The blockade and delays have had a chilling effect on commercial suppliers as ships pay hefty demurrage fees as they wait for unloading, experts say.

“The blockade of November and December has been solved in January, but really the ships from Djibouti to the harbor of Hodeidah started regularly only at the end of February,” said Dr. Nevio Zagaria, the World Health Organization’s envoy in Yemen.

But “bureaucratic impediments” still slow the aid flow, both at Hodeidah and Aden ports, he told Reuters.

“We are now early April, we still have the backlog of thousands of pallets that have been waiting to be transported,” Zagaria said, referring to medical and other supplies.