(Corrects headline and first paragraph to clarify what areas U.N. and aid groups are being asked to leave)

By Michelle Nichols

UNITED NATIONS, Feb 11 (Reuters) - Saudi Arabia, which is leading air strikes against rebels in neighboring Yemen, has warned the United Nations and international aid groups to protect staff by removing them from areas near rebel military bases, according to a letter that was seen by Reuters on Thursday.

A short note sent by the Saudi Embassy in London on Friday said the intention was to "protect the international organizations and their employees," presumably from coalition air strikes.

The Saudi ambassador to the United Nations in New York, Abdallah Al-Mouallimi, told Reuters that Riyadh sent the letter because, "We're just concerned for the safety of the U.N. staff and their humanitarian agencies.

"We want them to go away from areas that are obvious targets," he said.

Saudi Arabia leads a coalition of nine Arab countries that began a military campaign in March to prevent Iran-allied Houthi rebels from taking complete control of Yemen.

U.N. aid chief Stephen O'Brien acknowledged receipt of the note in a Sunday letter seen by Reuters and said the humanitarian community would continue to deliver aid across Yemen impartially on the basis of need.

He reminded Saudi Arabia of obligations under international humanitarian law to facilitate access for aid.

The Saudi mission to the United Nations responded on Monday that Riyadh would "do its utmost to continue to facilitate and support" humanitarian aid work in Yemen, while also clarifying its request for U.N. and international aid workers to leave areas close to Houthi bases for military operations.

"The coalition's request is consistent with its obligations under international humanitarian law and, in no way, can be misinterpreted to indicate any hindrance to humanitarian access and the delivery of humanitarian assistance in Yemen," it said.

The U.N. Security Council is due to discuss the humanitarian situation in Yemen on Tuesday at the request of Russia, diplomats said.

The Houthis and their allies, forces loyal to former Yemen President Ali Abdullah Saleh, accuse the coalition of launching a war of aggression.

Nearly 6,000 people have been killed since the coalition entered the conflict last March, almost half of them civilians.

U.N. sanctions monitors said in a report last month that the Saudi-led coalition has targeted civilians with air strikes and some of the attacks could be a crimes against humanity.

The panel of experts documented 119 coalition sorties "relating to violations of international humanitarian law" and said that "many attacks involved multiple air strikes on multiple civilian objects."

(Reporting by Michelle Nichols; Editing by Cynthia Osterman and Leslie Adler) ((michelle.nichols@thomsonreuters.com; +1 646 223 6117; Reuters Messaging: michelle.nichols.reuters.com@reuters.net; Twitter: @michellenichols))

Keywords: YEMEN WAR/SAUDI UN