A coalition of mostly Gulf countries led by Saudi Arabia launched an attack on Wednesday to recapture the Yemeni port city from the Iran-backed Houthi rebels.

Yemeni troops loyal to the internationally recognized exile government have begun pressing forward toward Hodeida airport, according to local commanders.

Warplanes and naval vessels hit Houthi targets in the early morning hours after the Houthis refused to leave the city, the exile government said. The United Arab Emirates (UAE) had issued a deadline for the rebel group to abandon the strategically important port.

Read more: Yemen: Fears mount as fighting focuses on port of Hodeida

Losing port would hurt the Houthis

The multi-pronged attack is the first time coalition forces have tried to retake control of a major city during the three-year conflict. It aims to cut off supplies to Houthi-controlled Sanaa, Yemen's capital city, to pressure rebel leaders to enter negotiations.

The Houthis would suffer a heavy defeat if they lose Hodeida, Jens Heibach, a research fellow and analyst at the German Institute of Global and Area Studies, told DW.

"It would be very hard or rather impossible for the Houthis to make up for all the supplies hitherto received via Hodeida," Heibach said, adding: "plus the Houthis would lose an important geostrategic port which they could use to, for instance, target coalition vessels."

The head of the Norwegian Refugee Council Jan Egeland told DW that the attack on the large port city "should not happen."

"This is like attacking Rotterdam," said Egeland, who also served as a humanitarian official in the UN.

"What is special about Hodeida is that it's a lifeline to most of the population who live in the north," Egeland told DW.  "If that is now destroyed in the fighting, we will lose the lifeline to millions and millions of people that are already on the brink of starvation."

Western powers have 'fingerprints all over' Yemen blockade

He also told DW that he would speak to representatives of the United Arab Emirates and the  Saudi Arabia and urge them to call a ceasefire and put Hodeida under UN management.

"I'm actually very surprised and disappointed that the United States, the United Kingdom, France, and all these powers – that have fingerprints all over this blockade against Yemen and are very close to Saudi and Emirati-led military coalition – have not been able to avert this attack," he said.

Houthi forces captured Hodeida and Sanaa in 2014, and the coalition intervened in the civil war one year later after Houthi forces ousted President Abed Rabbu Mansour Hadi. More than 10,000 people have been killed in the war, which is seen largely as a proxy conflict between Saudi Arabia and its regional rival Iran.

Heibach said the Houthis could pose a difficulty for the coalition if they decide to withdraw to the highlands in surrounding Hodeida. "As far I know it is utterly hard to lead a military campaign in mountainous terrain as it is more complicated to use heavy weapons," he said. "It would probably end up in guerrilla warfare which is almost impossible to win and which the Houthis are quite experienced in."

Read more:Why are EU countries reluctant to intervene in Yemen's war?

Attack could worsen humanitarian crisis

Saudi Arabia and the UAE have said recapturing the port would allow the coalition to bring in supplies to relieve millions of people throughout Yemen who are facing starvation and disease.

But Adam Baron, a visiting fellow at the European Council on Foreign Relations, told DW the assault risks doing the exact opposite.

"If this ends up being a quick battle with the port being restored quickly, that's one thing," he said. "If it ends up being an extended battle where the port is destroyed in the process, that's quite another."

The International Committee of the Red Cross (ICRC) and United Nations called on both sides to protect civilians in Hodeida.

ICRC spokeswoman Marie-Claire Feghali said the attack was "likely to exacerbate an already catastrophic humanitarian situation in Yemen."

"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," Lise Grande, UN humanitarian coordinator for Yemen, told Reuters news agency.

The organization warned the coalition against striking the city amid concerns a battle could worsen one of the world's worst humanitarian crises and cause some 250,000 deaths in a worst-case scenario. International UN officials were ordered to leave the city on Monday.

'Cut off the hands of Iran'

Saudi Arabia has accused the Houthis, who deny they are fighting for Iranian interests, of using Hodeida port to import Iranian weapons. Riyadh has said some of the weapons, including missiles, have been launched against Saudi territory.

"The liberation of Hodeida port is a turning point in our struggle to recapture Yemen from the militias that hijacked it to serve foreign agendas," Yemen's exiled government said.

"The liberation of the port," it said, "is the start of the fall of the Houthi militia and will secure marine shipping in Bab al-Mandab strait and cut off the hands of Iran, which has long drowned Yemen in weapons that shed precious Yemeni blood."