'Catastrophic' risk of death for 300,000 Yemeni children trapped by attack

Battle for Yemen's biggest port under way

Yemen's Iran backed Houthi rebels suffered 30 fatalities in the fighting, which took place two km from the Hodeida airport, south of the city, medical sources told AFP.

The United Nations is struggling to avert disruption to the port, the main lifeline for food aid to a country where 8.4 million people are on the verge of starvation, potentially the world's worst famine for generations.

It said the landing was being attempted in support of the coalition offensive to capture the port city of Al-Hudadayah. People fled by routes to the north and west. Hodeida is the main entry point for food and humanitarian aid for the entire country.

Responding to the early stages of the attack-which began with an estimated 30 Saudi airstrikes within half an hour, guided by USA military intelligence-Win Without War wrote on Twitter that the attack is "a dark moment of shame for the United States". "Some civilians are entrapped, others forced from their homes".

"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.

Saudi-owned Al Arabiya TV quoted witnesses describing "concentrated and intense" bombing near the port itself.

Foreign Secretary Boris Johnson said on Wednesday the British government was in contact with the alliance about ensuring its operations comply with global law on protecting civilians.

At dawn on Wednesday, the Saudi-led Arab coalition began the long-anticipated ground, naval, and air campaign against Houthi rebels in Hodeidah, trying to recapture the strategic port. The U.N. special envoy to Yemen, Martin Griffiths, has said the world body is talking to both sides to de-escalate.

He called on all parties to engage with United Nations efforts "to spare Hodeida any military confrontation" and "give peace a chance".

"It's actually surprising that an exodus has not happened yet", United Nations refugee chief Filippo Grandi told reporters in Geneva.

The Arab states say they will try to keep the port running.

A major battle could test that support, especially if many civilians are killed or supplies disrupted.

The U.S. has backed the Saudi Arabian and Emirati forces through diplomacy, selling them billions of dollars per year in arms and providing logistical support such as warplane refueling and military intelligence.

Previously, worldwide aid agencies voiced alarm over the "looming disaster,"stressing that a battle will jeopardize the delivery of the scarce humanitarian aid desperately needed by the civilian population". The Saudis and the United Arab Emirates - the two major actors in the coalition - have not commented on the claim.

Yemen's exiled government "has exhausted all peaceful and political means to remove the Houthi militia from the port of Hodeida", it said in a statement.

A Yemeni anti-Houthi military official said the alliance had brought to bear a 21,000-strong force.

Yemeni forces massing around Hodeida are a mix of local fighters, those loyal to President Abedrabbo Mansour Hadi, and supporters of the ex-head of state, Ali Abdullah Saleh.

Coalition sources said the alliance carried out 18 air strikes on Houthi positions on the outskirts of Hodeida on Wednesday. "The Saudi coalition has not advanced at all in Hodeidah".

The Arab states hope for a swift victory that would force the Iran-aligned Houthis to negotiate.