The Saudi-led military coalition fighting Yemen's Shia rebels bombed the airport in the rebel-held capital, Sanaa, on Tuesday, Yemeni officials said, though there were conflicting reports as to the extension of damage caused in the strike.

The United Nations said most of the airport remained intact and that it would be able to receive aid shipments once they restart — after the coalition loosens the blockade of the war-torn country as it had announced.

But Yemeni officials in Sanaa, which is held by the rebels known as Houthis, said the airport's runway and a ground navigation tower were damaged. Repair crews were already at work, they added, speaking on condition of anonymity as they were not authorized to talk to reporters.

Jamie McGoldrick of the UN Office for the Coordination of Humanitarian Affairs said UN staff had visited the airport and spoken with authorities there, and that its "runway, taxiway, ramp, terminal and air traffic control tower were not hit and are in good condition."

"This will have no impact on our operations once they resume," McGoldrick said in an email from Amman, Jordan.

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A Yemeni child receives treatment at a hospital in Hodeidah on Nov. 11. Famine and a cholera outbreak have been part of the fallout from the years-long war. (Abdo Hyder/AFP/Getty Images)

The U.S.-backed coalition has been at war with the Houthis, since March 2015. The coalition closed all Yemen air, land and sea ports last week in response to a rebel ballistic missile attack on Riyadh.

The coalition said on Monday that it would reopen ports in areas held by allied forces and loosen restrictions it had raised after the firing of the missile, which was intercepted near Riyadh's international airport.

However, McGoldrick said earlier in the day that there was "no indication" the coalition was actually lifting the blockade in line with its announcement.

He said that coalition announcements of the availability of two ports in southern Yemen are "helpful," but that the key need is access to the rebel-held Red Sea ports of Salif and Hodeida, closer to large population centres, which are currently inaccessible to UN aid shipments. Both ports are in rebel-held territory.

"We have some 21 million people needing assistance and seven million of those are in famine-like conditions and rely completely on food aid," McGoldrick said.

"The humanitarian impact of what is happening right now is unimaginable," he added.

Vaccine supplies running low

The Saudi-led coalition has said it will keep Hodeidah port closed until a UN verification programme is reviewed to ensure no weapons reach the Houthis. Iran denies arming the Houthis and blames the 2½-year conflict in Yemen on Riyadh.

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United Nations humanitarian coordinator in Yemen, Jamie McGoldrick, seen on Aug. 17, said the famine-like conditions in the country are being exacerbated by the blocking of essential routes. (Mohammed Huwais/AFP/Getty Images)

Humanitarian agencies had been successful in preventing famine and tackling a cholera outbreak that has sickened more than 900,000 people in six months and killed over 2,200.

The north of the country, home to 78 per cent of the population, had 20 days' stocks of diesel, crucial for pumping water and fighting cholera, and 10 days' stocks of gasoline, with no prospect of resupply soon, he said.

Yemen had commercial wheat stocks for three months for the entire population of 28 million and about 120 days of rice.

The UN children's agency UNICEF had only three weeks of vaccine supplies left in Yemen, and both UNICEF and the World Health Organization had shipments of essential medicines and vaccines blocked in Djibouti, McGoldrick said.

Meanwhile, the Islamic State group struck a fresh blow to Saudi-allied forces in the country's south, as a suicide car bombing early on Tuesday targeted security forces in Aden, killing at least six people and wounding scores.

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A Yemeni youth takes part in a demonstration calling for the Saudi-led coalition's blockade to be lifted on Monday in the rebel-held capital Sanaa. (AFP/Getty Images)

The ISIS-claimed attack took place at a building in the Sheikh Othman district in the central part of the city. Residents several kilometres away heard a large explosion and saw thick black smoke rising from the area.

The attack caused panic in this densely populated area, which is busy with schools, markets and street vendors.

According to medical officials, six soldiers were killed but officials believe the death toll will rise. The official spoke on condition of anonymity because they weren't authorized to speak to the media.

With files from Reuters