Hundreds of civilians have been killed as Yemen has been consumed by combat over the last few weeks, with clashes stretching from southern provinces around Aden to the border with Saudi Arabia in the north.

The Saudi-led coalition, which includes the Sunni monarchies on the Persian Gulf and is backed by the United States, began its offensive last week, largely in response to the Houthi push toward Aden. Saudi officials accuse the Houthis, a militia from northern Yemen that also controls Sana, the capital, of acting as a proxy for Iran.

The Houthis acknowledge an alliance with Tehran but insist that they are acting as an independent force. The coalition has threatened to escalate military action, perhaps with ground troops, if the Houthis do not capitulate.