At least 45 people have been killed in an explosion near a refugee camp in northwest Yemen, aid workers say.
Yemen’s Foreign Minister Riyadh Yaseen denied Saudi air strikes were to blame for the blast at the al-Mazrak camp.
The camp has been housing Yemenis displaced by the conflict between the Houthis and the central government since 2009.
Saudi Arabia began targeting Shia Houthi rebels last week in support of Yemen’s embattled president.
President Abrabbuh Mansour Hadi fled the country for the Saudi capital Riyadh, as rebels advanced on the port city of Aden, where he had taken refuge.
The International Organization for Migration (IOM) said 65 people were also wounded in the al-Marzak bombing.
But Mr Yaseen said “artillery strikes” by the Houthis were to blame for Monday’s deaths.
Aid agency Medecins Sans Frontieres (MSF) said 29 dead bodies and 34 injured people were taken to a hospital it operates near the camp.
“It was an air strike,” said MSF’s Middle East programme manager Pablo Marco.
Mr Marco said 500 new families had arrived at the camp over the past two days as fighting intensified across the country.
There were reports of further unrest in the south with rebel forces shelling the town of Daleh. A local government official said eight people had been killed.
There was also heavy fighting reported in Aden after rebels pushed into the city’s north-eastern suburbs.
The Houthis have said their aim is to replace President Hadi’s government, which they accuse of being corrupt.
Former President Ali Abdullah Saleh – whose supporters are fighting alongside the Houthis – has called for a truce.
But Saudi Arabia has vowed to defend Mr Hadi’s government through air strikes and has the backing of several Arab League members.
Abdul Malik al-Houthi, leader of Houthis, has refused to surrender to what he called the “unjustified aggression” by the Saudi authorities and their allies.
Shia power Iran, which Sunni-ruled Saudi Arabia accuses of backing the rebels, has also demanded an immediate halt to the strikes, which it said violated Yemen’s sovereignty.
The Houthis: Zaidi Shia-led rebels from the north, who seized control of Sanaa last year and have since been expanding their control
President Hadi: Fled to Saudi Arabia after rebel forces advanced on his stronghold in the southern city of Aden
Al-Qaeda in the Arabian Peninsula: Seen by the US as the most dangerous offshoot of al-Qaeda, AQAP opposes both the Houthis and President Hadi.
Islamic State: A Yemeni affiliate of IS has recently emerged, which seeks to eclipse AQAP