A "horrific" air strike on a Yemeni prison has left many dead or missing, aid workers said on Friday after a night of deadly bombing that underlined a dramatic escalation in violence.

Gruesome scenes came to light in Saada, heartland of the Huthi rebel movement, as rescue workers pulled bodies from destroyed prison buildings and piled up mangled corpses, according to footage released by the insurgents.

Further south in Hodeida, video footage showed bodies in the rubble and dazed survivors after an air attack from the Saudi Arabia-led pro-government coalition took out a telecommunications hub. Yemen suffered a nationwide internet blackout, a web monitor said.

Saada's hospital has received about 200 people wounded in the prison attack and "they are so overwhelmed that they cannot take any more patients", said Doctors Without Borders, known by its French acronym MSF.

"There are many bodies still at the scene of the air strike, many missing people," Ahmed Mahat, MSF head of mission in Yemen, said in a statement.

"It is impossible to know how many people have been killed. It seems to have been a horrific act of violence."

The strikes come five days after the Iran-backed Huthis claimed a drone-and-missile attack on the United Arab Emirates that killed three people and prompted warnings of reprisals.

The United Nations Security Council is due to meet at 1500 GMT on Friday in an emergency session on the Huthi attacks against the UAE, at the request of the Gulf state, which has occupied one of the non-permanent seats on the council since January 1.

The UAE is part of the Saudi-led coalition that has been fighting the rebels since 2015, in an intractable conflict that has displaced millions of Yemenis and left them on the brink of famine.

The coalition claimed the attack in Hodeida, a lifeline port for the shattered country, but did not say it had carried out any strikes on Saada.

Saudi Arabia's state news agency said the coalition carried out "precision air strikes... to destroy the capabilities of the Huthi militia in Hodeida".

Global internet watchdog NetBlocks reported a "nation-scale collapse of internet connectivity". AFP correspondents in Hodeida and Sanaa confirmed the outage.

AFP