An attack on a military training camp in western Yemen killed dozens of government soldiers and wounded at least 100 others.

Yemen's president warned the military on Sunday it needs to be on high alert and ready for battle following the mass-casualty attack he blamed on the Houthi rebels in the city of Marib.

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The attacks killed 73 people and left dozens wounded, two medical sources told Reuters News Agency, adding that a mosque in the camp was targeted as people gathered for prayer. News reports in Saudi put the death toll at 60.

Death tolls in Yemen's grinding conflict are often disputed.

Saudi-owned Al Hadath television broadcast a video it said showed the gruesome aftermath of the attack. Body parts can be seen on the floor, among shredded debris - blood pooled on the carpet and spattered against the walls.

The attack "confirms without [a] doubt that the Houthis have no desire for peace", President Abd-Rabbu Mansour Hadi said in a statement on Yemen's state news agency, Saba.

He denounced the Houthis as "a cheap Iranian tool in the region".

The Houthis did not immediately claim responsibility for Saturday's attack. They deny being puppets of Iran and say they are fighting a corrupt system.

The oil-rich province of Marib lies about 115 kilometres (70 miles) east of the Houthi-controlled capital, Sanaa. The city is a stronghold of the Saudi-led, US-backed coalition.

The missile attack was the bloodiest attack in Marib since the beginning of Yemen's long-running civil war, marking a military escalation in a rare spot of relative stability.

The assault "involved three missiles", said Al Jazeera's Mohammed Alattab, reporting from Sanaa.

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"The death toll is expected to rise," Alattab said.

Al Ekhbariya television quoted sources as saying the assault was carried out with ballistic missiles and drones.

Rising death toll

The United Nations envoy for Yemen, Martin Griffiths, condemned the attack as well as air strikes and ground assaults around the country.

"The hard–earned progress that Yemen has made on de-escalation is very fragile. Such actions can derail this progress", Griffiths said, urging parties to direct their energies into politics and away from the battlefield.

The attack on the military training camp followed a continuing barrage of assaults by Saudi-backed forces on Houthi targets east of Sanaa. Those attacks killed at least 22 people on both sides, according to officials.

Fighting in the Nihm region was also continuing on Sunday, a military source said according to Saba News Agency. "Dozens from the [Houthi] militia were killed and injured," the source added.

Yemen has been torn by violence and chaos since 2014 when the Houthis overran much of the country, including Sanaa.

The crisis escalated in March 2015 when the Saudi-UAE-led coalition launched a devastating air campaign aimed at rolling back Houthi territorial gains and restoring Hadi's government, which is now based in the southern port city of Aden.

The five-year war, which the United Nations says has caused the world's worst humanitarian crisis, is estimated to have killed tens of thousands of people and pushed the country to the brink of famine.

Both the Houthi rebels and Saudi-led coalition forces have been accused of war crimes and rampant human rights abuses in Yemen. Indiscriminate coalition air raids and rebel shelling have drawn widespread international criticism for killing civilians and hitting non-military targets.