By Mohammed Ghobari
ADEN, June 18 (Reuters) - Arab coalition aircraft bombarded Houthi fighters holed up at the airport of Yemen's main port Hodeidah on Monday as a senior alliance official said he hoped U.N. diplomacy could coax the Iran-aligned movement to cede the city to "save the population".
There are fears that a prolonged battle for the city, where the Houthis are dug in to protect critical supply lines from the Red Sea to their bastion in the capital Sanaa, could aggravate what is already the world's most urgent humanitarian crisis.
The Western-backed Arab alliance launched an onslaught on Hodeidah six days ago in order to turn the tables in a long- stalemated, proxy war between Saudi Arabia and Iran that has compounded instability across the Middle East.
The coalition intervened in Yemen's war in 2015 after Houthi rebels drove the internationally recognised government into exile. UAE forces are spearheading the Hodeidah offensive, now focused on the airport of the Red Sea city.
On Monday Apache helicopter gunships fired at Houthi snipers and other fighters positioned on the rooftops of schools and homes in the Manzar neighbourhood abutting the airport compound, according to local residents.
Houthi forces had blocked roads to the airport, they said.
The Houthis' al-Masira television reported six coalition air strikes on the Duraihmi district in the vicinity of the port.
The upsurge in fighting has wounded dozens of civilians and prevented aid organisations from reaching parts of Hodeidah.
In Geneva, U.N. human rights chief Zeid Ra'ad al-Hussein voiced concern the onslaught could cause "enormous civilian casualties and have a disastrous impact on life-saving...aid to millions of people which comes through the port".
A senior UAE official said the coalition was taking a measured approach to the battle to minimise risks to civilians and was allowing the Houthis an escape route inland to Sanaa.
In addition, 100 trucks of food aid were en route to Hodeidah on the road from coalition-controlled Aden and Mokha to the south, UAE Minister of State for Foreign Affairs Anwar Gargash told a news conference in Dubai.
"We have planned diligently around the humanitarian challenge. Our approach is methodical, gradual, calibrated to squeeze, to make a point, to allow the Houthis to do the right thing, which is basically decide to withdraw unconditionally."
The Houthis' days in Hodeidah were numbered, he said, and they needed to "as much as possible save the population".
He said the coalition was counting on Martin Griffiths, the U.N. special envoy for Yemen, to "pull a rabbit out of a hat" and secure Houthi agreement to vacate Hodeidah.
Griffiths returned to Sanaa on Saturday. Houthi authorities and the United Nations office in Sanaa said he would stay until Tuesday, after originally saying he would depart on Monday, hinting at possible progress in his discussions.
Gargash estimated the number of Houthi fighters in Hodeidah at between 2,000 to 3,000. "(They are) militia, non-descript, not in uniform, majority work in small groups, snipers, with heavy extensive use of anti-personnel and other mines."
Gargash declined to reveal the size of coalition forces but said they enjoyed "numerical superiority".
The Arab alliance has asserted that it can take Hodeidah quickly enough to avoid interrupting aid and that it would focus on capturing the airport and port and avoid street fighting.
STRONG HOUTHI HOLD ON HODEIDAH
But the coalition has not tried to capture such a heavily defended major city since entering the war, and humanitarian groups fear the battle for Hodeidah could drag out.
This would intensify the suffering of civilians who have already endured devastating air strikes, port blockades, hunger and a cholera epidemic.
Yehia Tanani said he and his family left Manzar three days ago and walked for 3 km (1.86 miles), hiding behind walls and under trees to avoid air strikes, before finding shelter at a fish farm. Others stayed to care for family members and cattle.
"They told us that some humanitarian organisations are going to send buses but then they said no buses could come in or out. So we started walking on foot carrying our children, sitting every while for rest while the Apaches hovered above us. We were scared not knowing if we'd be shot or not," he said.
"Now we're in this school, no mattresses, no electricity, no water, no bathrooms, nothing. And we have children who need medicine, need food, need anything, but we don't have anything," he said, sitting on the floor of an empty classroom of a school being used to house those displaced by the fighting.
Children slept on the floor of empty classrooms while others sat forlornly in the courtyard, where a few items of clothing and blankets were draped over balconies and upturned desks.
The coalition intervened in Yemen to thwart what Riyadh and Abu Dhabi see as efforts by Iran to dominate the region.
The Houthis, who rule the most populous areas of Yemen, a chronically unstable nation of 30 million people, deny being puppets of Iran and say their revolt is against corruption and defending Yemen from invaders.
(Additional reporting by Stephanie Nebehay in Geneva and Katie Paul in Riyadh Writing by Ghaida Ghantous Editing by Mark Heinrich)
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