The Saudi-led coalition backing Yemen's exiled government launched an assault Wednesday on the key port city of Hodeida.
Houthi rebels control Hodeida, as well as the Yemeni capital of Sana'a. The United Arab Emirates, a part of the coalition, said Wednesday marked the expiration of a deadline for the Houthis to leave the port.
Hodeida is crucial to bringing food and aid into Yemen. Even before the conflict between the Houthis and the government of Abdu Rabu Mansour Hadi began three years ago the country suffered from food insecurity, and the United Nations says more than 20 million people are now in need of aid.
The fighting has prevented consistent aid deliveries, and the exiled government said in a statement Wednesday that recapturing Hodeida would be a major milestone in the larger fight to reassert control over the country.
The United Nations estimates more than 10,000 people have been killed, most due to coalition airstrikes.
Last week, officials from the U.N.'s Office of the Coordination of Humanitarian Affairs expressed fears a military attack or siege on Hodeida would impact hundreds of thousands of innocent civilians.
Spokesman Jens Laerke said the United Nations and its partner agencies estimated there are as many as 600,000 civilians living in and around the city.