Yemeni troops backed by Arab Coalition forces began an assault to liberate the rebel-held Red Sea port city of Hodeidah on Wednesday in a bid to accelerate an end to the country's three-year war.
The UAE and Saudi Arabia had warned in recent days of increased military action and it started after the expiry of a midnight deadline for the Iran-backed Houthis to quit the city.
Four members of the UAE Armed Forces were reported to have died while performing their duties in Yemen. Their martyrdom was not initially linked to the latest operation.
The General Headquarters announced the martyrdom of the “brave servicemen” Sub-Lieutenant Khalifa Saif Saeed Al Khatri; First Warrant Officer Ali Mohammed Rashid Al Hassani; Sergeant Khamis Abdullah Khamis Al Zeyoudi; and First Corporal Obaid Hamdan Saeed Al Abdouli. It extended its condolences to their families.
The new operation, called Golden Victory, was launched after "exhausting all peaceful and political means", Yemen's government said in a statement.
The declaration was followed by airstrikes in and around Hoideidah port, hitting Houthi defences.
Residents of coastal villages and districts around southern Hodeidah had left their homes ahead of the fighting.
Yemeni officials said government forces had headed to the eastern coast, aiming to cut off a rebel supply line between Hodeidah and the Houthi-held capital Sanaa.
By Wednesday evening, Emirati and Saudi forces were five kilometres south of the city's airport. The centre of the city of 600,000 people lies four kilometres further north, and the seaport several kilometres beyond that.
Fierce clashes were taking place.
More on the Hodeidah offensive
Offensive for the liberation of Hodeidah enters second day - live updates
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Quoting medical sources in the province, the AFP news agency reported that 22 Houthi fighters had been killed over the past 24 hours by coalition raids. It also said three pro-government fighters were killed in a rebel ambush south of Hodeidah.
The Arab coalition intervened in the war in 2015 at the request of the internationally-recognised government of Yemeni President Abdrabu Mansur Hadi.
Wednesday's offensive was the first time since the coalition joined the war that they have attempted to capture such a well-defended city. Their aim is to box in the Houthis in Sanaa, cut their supply lines and force them to the negotiating table.
"We have been and continue to seek a peaceful solution," Mr Hadi said, backing the UN peace effort. "We made many concessions to avoid a military option. We however do not allow the exploitation of our people’s suffering and hold them hostages as a means to extend the war that the rebel militia has sparked."
Coalition air strikes targeting Houthi positions along the coast between Baiyt Al Faqih and Ad Durayhimi killed dozens of rebels on Wednesday, a local resident told The National.
The UN and International Committee of the Red Cross, meanwhile, said that all parties in Yemen’s war must protect civilians.
To that end pro-government and UAE forces were trying to secure routes for civilians to leave the city and reach safer areas.
Relief ships affiliated with the Coalition are placed off the coast, waiting to dock in Hodiedah.
Sulaiman Almazroui, the UAE's ambassador to Britain, rejected warnings that UN peace efforts were now caught up in the fate of Hodeidah.
"We don't think the capturing of Hodeidah will damage the peace. We think it will bring more pressure on the Houthis to sit down, rather than run away from the reality," he told The National in an interview.
Hodeidah's port handles 80 percent of essential goods coming into Yemen, which the United Nations says is grappling with the world's worst humanitarian crisis. Some 8.4 million people in Yemen face pre-famine conditions, according to the World Health Organisation.
The coalition, however, says the Houthis have used the port to smuggle Iranian-supplied weapons into the country but also to profit from illegally sold humanitarian aid.
Reem bint Ibrahim Al Hashimy, UAE minister of state for International Cooperation, said on Wednesday that the coalition had prepared a large-scale and comprehensive plan for the rapid delivery of humanitarian aid to Hodeidah and surrounding areas.
Hodeidah offensive could 'tip the balance' in stalemated Yemen conflict
"We have ships, planes, and trucks with food supplies and medicine to address the immediate needs of the people," she said in a statement.
"Hodeidah port remains open to shipping. Should the Houthis attempt to further damage and destroy any port or logistics infrastructure, we have also put contingency plans in place to move aid by other methods to Hodeidah and points beyond."
The Houthi militia has repeatedly fired missiles at Saudi Arabia, which the United States and UN experts say are of Iranian origin, a claim Tehran denies.
The early stages of Wednesday's offensive followed statements from UAE and Saudi officials that military action was necessary.
Prince Khaled bin Salman, Saudi Arabia's ambassador to the United States, said that the Houthi rebels had rejected all peaceful means to hand over Hodeidah.
"The Houthis have so far launched 150 ballistic missiles against civilian areas in KSA, latest of which was intercepted today…no nation can accept such a threat to its land and people on its borders," he tweeted in reference to the Kingdom of Saudi Arabia.
UAE Minister of State for Foreign Affairs Dr Anwar Gargash said on Tuesday he was "deeply concerned" by reports that Houthi rebels in Hodeidah were forcing civil servants and civilians to pick up arms.
Such action was "the Houthi response to international calls for their peaceful retreat," he added.
The United Nations pulled all of its international staff out of Hodeidah on Monday.
UN envoy to Yemen Martin Griffiths last week held several rounds of talks with the rebels in Sanaa. He is due to present a peace plan to the Security Council next week.
Yemen has been in crisis since the 2011 mass protests that ended then president Ali Abdullah Saleh's 33-year rule.
Mr Hadi came to power in a Saudi-brokered transition, but the Houthis drove him out. For a time Mr Saleh joined forces with the Houthis, but they turned on each other last year and the former president was killed. Parts of Yemen are also held by Al-Qaeda and ISIS.