Troops backed by a Saudi-led coalition on Wednesday launched an assault on Yemen's main port city of Hodeidah, in the biggest battle of a three-year war between an alliance of Arab states and the Iran-aligned Houthis.
Iranian-aligned Shia rebels known as Houthis and their allies for years have held the Red Sea port, crucial to food supplies in a nation on the brink of starvation after years of war.
Rebel positions are being bombarded from the air and sea, according to regional media. The sound of heavy, sustained gunfire could be heard clearly in the background.
Before the war, over 70% of Yemen's food and fuel imports came through Hodeidah, accounting for over 40% of the nation's customs income. The port remains crucial for incoming aid, food and medicine for a nation driven to the brink of starvation by the conflict and a Saudi-led blockade.
Saudi-owned satellite news channels later announced the battle had begun, citing military sources.
"Liberation of the port of Hodeidah is a milestone in our struggle", the statement reads. "Liberation of the port is the beginning of the fall of the Houthi militias".
Forces loyal to Yemen's exiled government and irregular fighters led by Emirati troops had neared Hodeida in recent days. The port is 150km (90 miles) south-west of Sanaa, Yemen's capital held by the Houthis since they swept into the city in September 2014.
UAE Junior Foreign Minister Anwar Gargash told the BBC that the coalition had run out of patience with diplomatic efforts after a previous 48-hour deadline expired.
The United Nations and other aid groups already had pulled their global staff from Hodeidah before the rumoured assault.
The civil war in Yemen has killed about 10,000 people over the past three years and created what the United Nations says is the world's worst humanitarian disaster. The Saudi-led coalition has been criticized for its airstrikes killing civilians. State media in both Saudi Arabia and the United Arab Emirates did not immediately acknowledge the assault.
The UN says some 600,000 people live in and around Hodeida, and "as many as 250,000 people may lose everything - even their lives" in the assault.