Dubai - More than 100 people were killed and dozens wounded in a missile and drone attack blamed on Houthi militia in central Yemen, officials said Sunday.

Saturday’s strike follows months of relative calm in the war between the Houthis and Yemen’s internationally recognized government.

The Houthis attacked a mosque in a military camp in the central province of Marib — about 170 kilometers (105 miles) east of the capital Sanaa — during evening prayers.

“We strongly condemn the terrorist attack on a mosque by the Houthi militias... which left more than 100 dead and dozens injured,” the Yemeni foreign ministry said on Twitter.

An army spokesman said that the dead included soldiers and civilians, and that the Houthis would face a “ruthless” retaliation to the strike.

The victims were transported to a Marib city hospital, where a medical source earlier gave a toll of 83 dead and 148 injured.

Death tolls in Yemen’s grinding conflict are often disputed, but the huge casualty list in Marib represents one of the bloodiest single attacks since the war erupted in 2014 when the terrorist militia seized Sanaa.

The Houthis did not make any immediate claim of responsibility.

Saudi-owned Al-Hadath television broadcast a video that it said showed the gruesome aftermath of the attack.

Body parts can be seen on the floor among shredded debris. Blood is pooled on the carpet and spattered against the walls.

The drone and missile strike came a day after coalition-backed government forces launched a large-scale operation against the Houthis in the Nihm region, north of Sanaa.

Fighting in Nihm was ongoing on Sunday, a military source said according to the official Saba news agency.

“Dozens from the (Houthi) militia were killed and injured,” the source added.

Yemeni President Abedrabbo Mansour Hadi denounced the “cowardly and terrorist” attack on the mosque, Saba reported.

“The disgraceful actions of the Houthi militia without a doubt confirm its unwillingness to (achieve) peace, because it knows nothing but death and destruction and is a cheap Iranian tool in the region,” it quoted Hadi as saying.

United Nations envoy Martin Griffiths condemned the aerial attack and what he said was the escalation of military activities in three governorates “where airstrikes, missiles and ground attacks reportedly took place.”

“I have said before that the hard-earned progress that Yemen has made on de-escalation is very fragile. Such actions can derail this progress,” he said in a statement.

“I urge all parties to stop the escalation now and to direct their energy away from the military front and into the politics.”

Just last week Griffiths had welcomed what he described as “one of the quietest periods of this conflict,” in a briefing to the UN Security Council in which he warned the lull could not be sustained without political progress.