The United Nations and other aid groups already had pulled their global staff from Hodeidah before the rumoured assault.
Hodeidah, Yemen's biggest port and the only port controlled by the Houthis, serves as the lifeline for the majority of Yemen's population, which lives in Houthi-ruled territory.
A source from the Yemeni National Resistance said that a large number of forces from Brigades AlAmalaqah and the Tihama Resistance Forces, armed with modern weapons and in high morale, have arrived at the outskirts of Al Hodeidah city to continue their build-up in the front lines in preparation for the battle of rolling back the Houthi militias and putting and end to the coup plot in Yemen.
The United Nations had been trying to get the parties to reach a deal that would avert an attack on Hodeidah, which it fears would further impede Yemenis' access to food, fuel and medicine, exacerbating the world's most urgent humanitarian crisis in the impoverished Arab state.
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.
The Hudaida port is crucial for the flow of food supplies into a country that is on the brink of starvation.
The Saudi-led coalition did not immediately acknowledge the incident.
The assault is the first time since the Western-backed coalition of mostly Gulf states joined the war in 2015 that they have attempted to capture such a well-defended major city.
Un jeune pilote espagnol décède en course — Carnet
Résident à Mollet, près du circuit barcelonais, Andreas avait débuté la moto à 3 ans avant de débuter la compétition à 7 ans. Un autre concurrent ne parvenait pas à l'éviter et le percutait de plein fouet.
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.
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.
Washington had also cautioned against the assault.
Defense Secretary Jim Mattis on Monday acknowledged the United States continues to provide support to the Saudi-led coalition.
The air strikes on Wednesday morning targeting Houthi positions are supported by ground operations by Yemeni troops south of the Red Sea port, the internationally recognised Yemeni government-in-exile said in a statement.
The Houthis, with roots in a Zaidi Shi'ite minority that ruled a thousand-year kingdom in Yemen until 1962, deny they are pawns of Iran.
Yemen lies beside the southern mouth of the Red Sea, one of the most important trade routes in the world for oil tankers, which pass near Yemen's shores while heading from the Middle East through the Suez Canal to Europe.
He said the coalition wanted the United Nations to take control of the port but it was prepared to take military action if the Houthis refused to withdraw.
Riyadh says the Houthis use the port to smuggle Iranian-made weapons, including missiles that have been launched at Saudi cities - accusations denied by the group and Tehran.
The president said the drills cost the US a " tremendous amount of money ", and that South Korea hasn't always chipped in enough. CBS News' David Martin reports that Pentagon spokesperson Dana White said Defense Secretary James Mattis "was not surprised".
Pour rappel, l'équipe de France débutera sa Coupe du monde face à l'Australie le samedi 16 juin à 12h. Mbappé a également pris la défense de son coéquipier Adil Rami qui l'a percuté lorsqu'il s'est blessé.
More importantly, he would head to Shinnecock Hills with a spring in his step for the second major championship of the year. At the 445-yard par-4 sixth, Bryan got on in 2 and missed his par putt from 4 feet, finishing with a 3-putt bogey.
Among them is T-Mobile US, which is waiting for a government decision on their proposed merger with Sprint Corp . Leon said the government failed to prove that the merger would lead to higher prices and other ham to consumers.
Opposée à Madison Keys , l'Américaine s'est imposée en deux manches bien menées: 6-4, 6-4 et 1h19 de jeu. Del Potro a eu quelques occasions en début de match pour réaliser une percée au service de Nadal .
PM Modi had earlier on Wednesday invited Kumaraswamy to take up the fitness challenge which is doing the rounds on Twitter. PM Modi responded to Virat Kohli's challenge and tweeted using the hashtag #HumFitTohIndiaFit .
L'Espagnol a parfaitement commencé et fini ce set, ne laissant que l'Autrichien l'accrocher en milieu de première manche. Nadal est resté imperturbable sur ses mises en jeu et s'est même permis de briser son adversaire (5-2).
England face Tunisia in their opening Group G fixture on Monday, before taking on Panama and Belgium . England boss Gareth Southgate has revealed that Marcus Rashford has sustained an injury to his knee.
Justify bags Triple Crown win in Belmont Stakes
But it's a challenge Gunther welcomes. "He's got such a natural high cruising speed and he can just kind of keep on going". If he stays in the east, Justify now goes on to either the Grade 1 Haskell at Monmouth Park or the Jim Dandy at Saratoga.