The UN Security Council will meet on Thursday for urgent talks following the launch of an offensive on the port city, which is a lifeline for humanitarian aid to millions who are on the brink of famine.
A Saudi-led coalition backing Yemen's exiled government began an assault on Wednesday morning on Yemen's port city of Hudaida.
Aid agencies warned that the crucial battle in the three-year-old conflict could push the Arab world's poorest country into further chaos.
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 famine after years of war.
TRT World's Staci Bivens reports.
The battle for Hudaida, if the Houthis don't withdraw, also may mark the first major street-to-street urban fighting for the Saudi-led coalition, which can be deadly for both combatants and civilians alike.
Before dawn on Wednesday, convoys of vehicles appeared to be heading toward the rebel-held city, according to videos posted on social media. The sound of heavy, sustained gunfire clearly could be heard in the background.
The initial battle plan appeared to involve a pincer movement. Some 2,000 troops who crossed the Red Sea from an Emirati naval base in the African nation of Eritrea landed west of the city with plans to seize Hudaida's port, Yemeni security officials said.
Emirati forces with Yemeni troops moved in from the south near Hudaida's airport, while others sought to cut off Houthi supply lines to the east, the officials said. They spoke on condition of anonymity as they weren't authorised to brief journalists.
TRT World's Editor-at-large Ahmed al-Burai explains what's behind the Hudaida assault.
The UN Security Council will meet Thursday for urgent talks following the launch of the offensive on the port city, a lifeline for aid, by government forces backed by the Saudi-led coalition, diplomats said.
Britain requested the meeting to be held behind closed doors at 1600 GMT, marking the second time this week that the council will have met on the crisis in Yemen.
UN Yemen envoy "extremely concerned"
The United Nations Special Envoy to Yemen, Martin Griffiths, has called on the warring sides to avoid a battle for the port city and return to the negotiating table.
"I am extremely concerned about military escalation in #Hodeida & their humanitarian & political impact," he said in a tweet.
"We're in contact with parties to avoid further escalation. We call on them to exercise restraint & engage with political efforts to spare Hodeida a military confrontation."
Early morning assault
Saudi-owned satellite news channels and later state media announced the battle had begun, citing military sources.
Yemen's exiled government "has exhausted all peaceful and political means to remove the Houthi militia from the port of Hudaida," it said in a statement. "Liberation of the port of Hudaida is a milestone in our struggle to regain Yemen from the militias."
The Houthi-run Al Masirah satellite news channel later acknowledged the offensive, claiming rebel forces hit a Saudi coalition ship near Hudaida with two land-to-sea missiles. Houthi forces have fired such missiles at ships previously.
"The targeted ship was carrying troops prepared for a landing on the coast of Hudaida," the channel said. The Saudi-led coalition did not immediately acknowledge the incident.
Forces loyal to Yemen's exiled government and irregular fighters led by Emirati troops had neared Hudaida in recent days. The port is some 150 kilometres (90 miles) southwest of Sanaa, Yemen's capital held by the Houthis since they swept into the city in September 2014. The Saudi-led coalition entered the war in March 2015 and has received logistical support from the United States.
Emirati Minister of State for Foreign Affairs Anwar Gargash earlier told French newspaper Le Figaro the deadline for a withdrawal from Hudaida by the Houthis expired early on Wednesday morning.
The United Nations and other aid groups already had pulled their international staff from Hudaida ahead of the expected assault.
The UN and the International Committee of the Red Cross (ICRC) called on Wednesday for all sides to protect civilians.
ICRC spokesperson Iolanda Jaquemet spoke to TRT World.
"Under international humanitarian law, parties to the conflict have to do everything possible to protect civilians and ensure they have access to the assistance they need to survive," said Lise Grande, the UN's humanitarian coordinator for Yemen.
Over 10,000 people have been killed in Yemen's civil war, which has displaced two million more and helped spawn a cholera epidemic.
The Saudi-led coalition has been criticised for its air strikes which have killed civilians.
Meanwhile, the UN and Western nations say Iran has supplied the Houthis with weapons from assault rifles up to the ballistic missiles they have fired deep into Saudi Arabia, including at the capital, Riyadh.
Before the war, over 70 percent of Yemen's food and fuel imports came through Hudaida, accounting for over 40 percent of the nation's customs income.
Crucial for aid
The port city of Hudaida is crucial for incoming aid, food and medicine for a nation driven to the brink of famine by the conflict and a Saudi-led blockade. A Saudi-led airstrike in 2015 destroyed cranes at Hudaida.
The United Nations in January shipped in mobile cranes to help unload ships there.
The UN says some 600,000 people live in and around Hudaida, and "as many as 250,000 people may lose everything – even their lives" in the assault.
"We have had more than 30 airstrikes within 30 minutes this morning around the city. Some civilians are entrapped, others forced from their homes," said Jolien Veldwijk, the acting country director of the aid group CARE International, which works in Hudaida.
"We thought it could not get any worse, but unfortunately we were wrong."
UN Secretary-General Antonio Guterres had said that UN envoy Martin Griffiths was in "intense negotiations" in an attempt to avoid a military confrontation.
However, Griffiths' recent appointment as envoy and his push for new negotiations may have encouraged the Saudi-led coalition to strengthen its hand ahead of any peace talks with the Houthis.
Defense Secretary Jim Mattis on Monday acknowledged the US continues to provide support to the Saudi-led coalition.
"It's providing any intel, or anything we can give to show no-fire areas where there are civilians, where there's mosques, hospitals, that sort of thing – [and] aerial refuelling, so nobody feels like I've got to drop the bomb and get back now," he said.