At least 30 people are reported to have been killed in Saudi-led coalition air strikes on a rebel military police camp in Yemen's capital, Sanaa.
Most of the dead were said to be detainees at a prison inside the camp.
A guard said an initial attack damaged one wing of the jail, prompting some inmates to try to escape. Then another strike almost demolished the building.
The coalition backs Yemen's government in its war against the Houthi rebel movement.
More than 8,670 people have been killed and 49,960 injured since the coalition intervened in the conflict in 2015, according to the UN.
The fighting and a blockade by the coalition has also left 20.7 million people in need of humanitarian aid, created the world's largest food security emergency, and led to a cholera outbreak that is thought to have killed 2,219 people since April.
The raid on the camp in eastern Sanaa began in the early hours of Tuesday.
One of the guards at the camp's prison, Mohammed al-Aqel, told AFP news agency that it was hit at least five times, and that several buildings and a perimeter wall were heavily damaged.
An official told Reuters news agency that about 180 people were being detained at the jail, and that 35 bodies had so far been pulled from the rubble.
The Houthis' Al-Masirah TV put the death toll at 30 and said all of those who died were prisoners.
There was no immediate comment from the coalition.
However, it has carried out a series of air strikes on Houthi positions in Sanaa since clashes erupted two weeks ago between Houthi fighters and supporters of their former ally, ex-President Ali Abdullah Saleh.
Saleh was killed in an attack outside Sanaa on 4 December, two days after he declared that he was breaking with the Houthis and that he was ready to "turn a new page" with the Saudi-led coalition if it stopped attacking Yemen.
The street fighting in Sanaa trapped civilians in their homes for days and left at least 234 people dead, according to the International Committee of the Red Cross.
On Sunday, security sources told AFP that coalition air strikes on a Houthi training camp in Hajja province, north-west of the capital, had killed 26 rebels.