The Saudi government has sent letters to the United Nations and to aid agencies operating in Yemen, stating that they should leave areas under Houthi control in order to be safe from bombing, VICE News can reveal.

An initial letter was sent by the Saudi mission in Geneva on February 5 to the UN's Office for the Coordination of Humanitarian Affairs (OCHA). The "note verbale" — French for "verbal note," a kind of diplomatic communication — requested that OCHA "notify all the international organizations working in Yemen about the necessity of relocating their headquarters outside the military operations areas to be away from regions where the Houthi militias and the groups belonging to them are activating, in order for the Coalition forces to guarantee the safety and security of the international organizations." A similar letter, addressed to "International Organisations and their employees," and marked "urgent," was sent out on the same day by the Saudi embassy in London.

Houthi rebels and their allies loyal to former President Ali Abdullah Saleh control areas where the majority of Yemen's population lives, including the capital Sanaa, where most aid organizations and UN operations are headquartered.

A blistering Saudi-led air war, launched last March, has caused the majority of more than 2,700 civilian deaths since then, according to the UN. Yemen was already the poorest country in the Arab world before the war; now, OCHA has reported that more than 21 million people in Yemen require some form of humanitarian assistance. That's most of the country of 24 million. In addition to UN agencies, many private nonprofit organizations — both international and local — are operating in the country and providing aid to millions of Yemenis.

On February 7, OCHA chief Stephen O'Brien responded to the note verbale in a letter to to Abdallah al Mouallimi, Saudi Arabia's ambassador to the United Nations in New York.

"The humanitarian community is delivering life-saving assistance, as per internationally recognized principles across Yemen and will continue to do so impartially and on the basis of need," wrote O'Brien. "For the past nine months the United Nations has been using the Saudi established de-confliction mechanism through the United Nation's De-confliction Liaison Team based in Riyadh, and we will continue to use this mechanism to inform the Kingdom of Saudi Arabia of all humanitarian staff and supply movement, including those to and from the sub-national offices in Sa'da, Hudaydah, Ibb and Aden."

"I remind the Kingdom of Saudi Arabia of their obligations under international humanitarian law to facilitate humanitarian access, as well as their duty of care obligations under the conduct of military operations for all civilians, including humanitarian workers," said O'Brien.

The following day, February 8, Mouallimi wrote to O'Brien, attempting to clarify the intent of the initial letter. Mouallimi narrowed the Saudi appeal, writing that the Riyadh-led coalition in Yemen "requested that humanitarian and relief organizations relocate from areas close to bases for military operations by Houthis and supporters of former President of Yemen, Ali Abdullah Saleh."

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

VICE News obtained all three letters and confirmed their dissemination with multiple UN employees both in New York and Yemen, as well as with aid workers who received them through NGO coalitions that help coordinate aid efforts around the world. While some UN officials said they were still attempting to parse the intent of the Saudi letters, others, as well as aid workers and staff at human rights organizations, described them as sending an alarming message.

"This note verbale is very clear in my view, it is telling humanitarian organizations to get the hell out, before the coalition makes a full assault on the capital and other areas under Houthi control," said Belkis Wille, Yemen researcher at Human Rights Watch, who reviewed the letters. "The coalition's message suggests that they are trying to absolve themselves of their responsibility to facilitate humanitarian access, and be vigilant in distinguishing between military and civilian objects in their operations."

Noting that that three hospitals supported by the medical charity Doctors Without Borders, as well as dozens of civilian sites, have been hit by Saudi-led aircraft, Wille said the Saudi communication "unfortunately befits the tone of the coalition's level of commitment towards abiding by the laws of war."

VICE News reached out to OCHA for comment on ongoing dialogue between its office and the Saudi government, as well as to the Saudi mission to the UN to clarify the intent of the letters. At the time of publication, neither had replied.

Throughout the intervention it has led in Yemen, the Saudi government has had a rocky relationship with the UN and humanitarian agencies operating in the country. In April, the Saudis promised $274 million to the UN, meeting its "flash appeal" for help for Yemen. The bulk of that assistance was not delivered until the fall, and aid workers described communications with the Saudis as painstaking. Riyadh insisted on a drawn-out negotiating process, in which it reached individual memoranda of understanding with each of the UN's recipient aid agencies. Those memoranda have still not been made public.

In early January, the Saudi-backed government of President Abd Rabbuh Mansur Hadi declared the UN's top human rights official for Yemen "persona non grata." That declaration came just days after the UN's Office of the High Commissioner for Human Rights released multiple accounts of Saudi-led strikes killing civilians, which staff at OHCHR said privately had clearly angered the Saudis. Similarly, aid workers that VICE News spoke with said the letters sent last week followed a pattern of Saudi officials lashing out at international organizations and the UN. (After the move was condemned by the UN, Yemeni officials reversed their decision about the UN's human rights official.)

"In essence the Saudi argument is more or less [that] we are interested in protecting humanitarian action by kind of warning people or asking people to stay out of harm's way, but it obviously begs the question of the overall conduct of the war that we've seen since the beginning of the conflict," said Joel Charny, humanitarian vice president at InterAction, an umbrella group of relief and development NGOs.

"The issue is not humanitarians in the way, the issue is the way the Saudis are conducting the war," said Charny. "The implication of the Saudi approach is: If you're hit, it's your fault."

Other humanitarian workers that VICE News spoke with who had seen the letters said that while it may not indicate the Saudi coalition intends to endanger aid staff, they followed a pattern of problematic messaging issued by Saudi diplomats. All of the sources VICE News consulted said the letters were at best ambiguous.

A man walks past a destroyed hotel used by Houthi fighters after it was hit by airstrikes carried out by the Saudi-led coalition in Sana'a, Yemen, 31 May 2015. Photo by Yahya Arhab/EPA

Aid workers in Yemen have previously confirmed to VICE News that the Houthis and their allies also put civilians in danger, by moving military vehicles and weapons in civilian areas. In January, a panel of experts appointed by the Security Council to monitor sanctions in Yemen reported that the Houthis had on more than one occasion gone so far as to use African migrants "as human shields" in buildings that had previously been targeted by airstrikes, or where weapons caches were claimed to be stored." The Houthis and forces loyal to Saleh have also been documented obstructing aid deliveries, firing indiscriminately into residential areas and killing hundreds, as well as laying mines as they retreat from areas in the south of Yemen, including the port city of Aden.

In the same report, the panel said it had documented 119 coalition airstrikes "relating to violations of international humanitarian law." Among the targets hit by the Saudi-led coalition, the panel wrote, were "camps for internally displaced people and refugees; civilian gatherings, including weddings; civilian vehicles, including buses; civilian residential areas; medical facilities; schools; mosques; markets, factories and food storage warehouses."