Saudi-led coalition air strikes on rebel-held security buildings in western Yemen have killed at least 60 people, many of them inmates buried under the rubble of their detention centre.

The strikes late Saturday came just hours after other coalition raids hit three residential buildings in the southwest of the country, killing 17 civilians.

Yemen's President Abedrabbo Mansour Hadi on Saturday rejected a UN peace proposal aimed at ending his country's 19-months conflict against the Shiite Huthi rebels and their allies.

Forces loyal to Hadi's government have been locked since 2014 in deadly battles with the rebels, who seized the capital Sanaa late that year.

The conflict escalated in March 2015 when the Saudi-led coalition launched a military campaign to push back the rebels, after they advanced from the capital including towards the coastal province of Hodeidah.

In the latest deadly strikes in Hodeidah, which the rebels have controlled since late 2014, coalition warplanes hit a rebel-held security compound in the town of Zaidia.

“Sixty people in total were killed and dozens were wounded,” a health official said.

Most of the victims were anti-rebel detainees who were being held among 100 inmates in two cells at the detention centre, he said.

It remains unclear why the coalition would hit a detention centre holding anti-rebel inmates.

'Lack of medical supplies'

AFP footage from the site showed the bloodied limbs and bodies of the victims covered in dust and buried under the rubble as sirens wailed nearby.

“We were about to go to sleep when an air strike targeted us,” said a wounded man at a hospital in the area.

“We ran away and a second air strike hit us again,” he said, as medics rushed around bringing in wounded victims covered in blood.

The rebel-controlled sabanews.net also gave a toll of 60 killed and 38 wounded, adding that “dead bodies are still being retrieved” from under the rubble.

Coalition warplanes hovering over the area “are hampering attempts to save the victims and retrieve bodies,” sabanews.net reported.

International aid groups have repeatedly voiced concern over the rising need for aid in Yemen, where malnutrition has increased in the past months.

“The number of victims could rise further due to the lack of medical supplies,” it said, quoting a medical source who blamed the coalition's “blockade”.

A lack of ambulances “has made attempts to transfer critical cases to hospitals in the city of Hodeidah more difficult,” the source said.

UN 'rewards putschists'

Elsewhere on Saturday, strikes killed 17 civilians and completely destroyed three residential buildings in a town southeast of third city Taez, sabanews.net said.

A local official loyal to Hadi's government said the air strikes had hit three adjacent homes by mistake. But the coalition -- which has is under pressure over the high civilian death toll from its bombing campaign -- has so far not commented on either of the attacks.

The conflict has killed nearly 7,000 people, mostly civilians, since March 2015, according to the United Nations, which has been struggling to convince the warring parties to implement a ceasefire and revive a stalled political process.

The rebels are allied with troops who have remained loyal to former president Ali Abdullah Saleh.

Hadi rejected the latest peace proposal submitted by UN envoy Ismail Ould Cheikh Ahmed on Saturday.

The contents of the roadmap, which the envoy presented to the rebels on Tuesday, have not been made public.

But informed sources say the plan calls for agreement on naming a new vice president after the rebels withdraw from Sanaa and other cities and hand over heavy weapons to a third party.

Hadi would then transfer power to the vice president who would appoint a new prime minister to form a government in which the north and south of Yemen would have equal representation.

The president has slammed the UN proposal as one that “rewards the putschists while punishing the Yemeni people and legitimacy”.