A Yemeni woman sits next to her sleeping child at a temporary shelter after fleeing violence in Yemen, at the port town Bosasso in Somalia's Puntland. April 17, 2015. (REUTERS/Feisal Omar)

A group of 18 Yemen scholars and experts based in the United States and Britain published an open letter decrying the near month-long Saudi bombing campaign in the country. The letter, whose signatories include academics at Harvard, Oxford and Columbia universities, argued the Saudi-led war "is illegal under international law" and urged American and British officials to push for a U.N. Security Council resolution "demanding an immediate, unconditional ceasefire."

According to the United Nations, more than three weeks of Saudi airstrikes and renewed clashes between rival factions on the ground have led to the deaths of some 750 Yemenis and more than 150,000 being forced to flee their homes.

There are fears of humanitarian catastrophe. "The targets of the campaign include schools, homes, refugee camps, water systems, grain stores and food industries," warns the letter. "This has the potential for appalling harm to ordinary Yemenis as almost no food or medicine can enter."

The Saudi intervention followed the steady collapse of the government of President Abed Rabbo Mansour Hadi, who came to power with Saudi backing in 2012. A rebellion led by the Houthis, a Shiite political movement, seized Yemen's capital Sanaa last year. Hadi fled his sanctuary in the southern city of Aden last month as Houthi forces approached and is now in Riyadh.

A complex, local conflict has been overshadowed by the narrative of a regional proxy war between Saudi and Iranian interests. The Saudis, as well as Hadi, accuse the Houthis of being Iranian puppets. Some analysts say the connection between Tehran and the Houthis has been exaggerated.

American officials are believed to be displeased with the Saudi action; it's not clear quite what the Saudi endgame is now that a sustained military campaign is underway.

All the while, Yemen is unraveling as both a state and a nation, with a host of militias -- including al-Qaeda's Yemeni wing -- warring over what remains.

The full letter reads as follows:

We write as scholars concerned with Yemen and as residents/nationals of the United Kingdom and the United States. The military attack by Saudi Arabia, backed by the Gulf Cooperation Council states (but not Oman), Egypt, Jordan, Sudan, the UK and above all the US, is into its third week of bombing and blockading Yemen. This military campaign is illegal under international law: None of these states has a case for self-defense. The targets of the campaign include schools, homes, refugee camps, water systems, grain stores and food industries. This has the potential for appalling harm to ordinary Yemenis as almost no food or medicine can enter. Yemen is the poorest country of the Arab world in per capita income, yet rich in cultural plurality and democratic tradition. Rather than contributing to the destruction of the country, the US and UK should support a UN Security Council resolution demanding an immediate, unconditional ceasefire and use their diplomatic influence to strengthen the sovereignty and self-government of Yemen. As specialists we are more than aware of internal divisions within Yemeni society, but we consider that it is for the Yemenis themselves to be allowed to negotiate a political settlement.

Robert Burrowes, University of Washington

Steve Caton, Harvard University

Sheila Carapico, University of Richmond

Paul Dresch, University of Oxford

Najam Haidar, Barnard College

Helen Lackner

Anne Meneley, Trent University

Brinkley Messick, Columbia University

Flagg Miller, University of California-Davis

Martha Mundy, London School of Economics

Thanos Petouris, SOAS-University of London

Lucine Taminian, The American Academic Research Institute in Iraq

Gabriele vom Bruck, SOAS-University of London

Lisa Wedeen, University of Chicago

Shelagh Weir

John Willis, University of Colorado

Stacey Philbrick Yadav, Hobart and William Smith Colleges

Sami Zubaida, Birkbeck College, London

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