Fierce fighting has been reported after pro-government forces in Yemen, backed by a Saudi-led coalition, launched an offensive on the rebel-held city of Hudaydah, a key port for aid supplies.
The United Arab Emirates confirmed of its four soldiers had been killed and 22 Houthi rebels reportedly also died.
Fighting raged mainly near the city's airport and the al-Durayhmi area south of the city, media reports say.
The UN Security Council is to hold urgent talks on Yemen on Thursday.
It is the first time the Saudi-led coalition of mostly Gulf states has tried to capture such a well-defended major city in Yemen.
About eight million people are at risk of starvation in the war-torn country and the coastal city is where most aid arrives for people in rebel-held areas.
The Emirati news agency Wam said attacking forces had managed to "liberate areas... in the surroundings of the airport" and captured or killed "dozens" of Iranian-backed Houthis.
It reported the "martyrdom" of the four Emirati soldiers but did not give further details of the fighting.
Medical sources in the region said 22 Houthi fighters had been killed in coalition strikes.
Coalition sources say 18 air strikes were carried out on Houthi positions on the outskirts of Hudaydah on Wednesday.
Houthi rebels, meanwhile, said they had struck a coalition warship with missiles although there was no confirmation of this.
The offensive, which analysts say could be the biggest battle so far in the Yemeni civil war, has raised fears of mass casualties among the city's 400,000 population.
However, coalition spokesman Colonel Turki al-Malki said they wanted to avoid a street war with the Houthis "for the safety of civilians".
He told al-Hadath TV that the aims were to win control of the airport and seaport as well as the main road leading to the capital of Sanaa.
Thursday's meeting of the UN Security Council was called by Britain amid fears of a humanitarian crisis in Hudaydah.
The pro-government assault began after Houthi rebels ignored a deadline to withdraw.
Civil war has raged in Yemen since late 2014, when the Houthis and allied forces seized north-western parts of the country, including the capital Sanaa, and eventually forced President Abdrabbuh Mansour Hadi to flee abroad.
Alarmed by the rise of a group they saw as an Iranian Shia Muslim proxy, Saudi Arabia and eight other Sunni Arab states launched a military campaign in March 2015 to restore Mr Hadi's government.