An airstrike on a prison in northern Yemen killed at least 60 people and wounded 200 more, while a separate attack shut down the country’s internet, as Saudi-led reprisals to a Houthi drone attack on the United Arab Emirates intensified.

The violence marked an especially deadly day in the seven-year war, leaving bystanders searching through rubble with their bare hands to rescue those trapped in two locations: a prison in the city of Sa’ada and a telecommunications centre in the port city of Hodeidah, where three children playing football nearby were reported to have been killed.

The prison in Sa’ada, which has been used as a detention centre for migrant workers transiting through Yemen, was the scene of even more devastation, with dozens of men reported buried in the rubble after jets struck at about 2.30am. By nightfall, workers were still trying to remove debris to reach those still trapped.

Overwhelmed nearby hospitals said they had been forced to turn away some of the injured.

“From what I hear from my colleague in Sa’ada there are many bodies still at the scene of the airstrike, many missing people,” said Ahmed Mahat, the Médecins Sans Frontières head of mission in Yemen. “It is impossible to know how many people have been killed. It seems to have been a horrific act of violence. Al-Gumhourriyeh hospital in the city has so far received around 200 wounded and they say that they are so overwhelmed that they cannot take any more patients.”

The downing of Yemen’s internet marks another low in a conflict that rivals the Syrian war as the most devastating humanitarian disaster in the world.

“News of the Saudi air strike on a prison – a protected civilian site – and knocking out Yemen’s internet is both tragic and no surprise,” said Mary Ellen O’Connell, a professor at Notre Dame law school in the US. “President Biden indicated at his press conference (on 19 January) that he would not be making every effort to end the Yemen civil war. The war has been catastrophic for civilians. The US has a duty to end it, following principles of international law. That means ending support for Saudi attacks.”

Yemen’s civil war began in 2014 when the Houthi descended from their base in Sa’ada to overrun the capital, Sana’a, prompting Saudi-led forces to intervene to prop up the government the following year.

Saudi jets have sharply stepped up attacks across Houthi-held parts of Yemen this week in the wake of a drone attack on Monday in Abu Dhabi that was claimed by the Houthi leadership. The strikes on an oil production plant and the nearby international airport killed three people and wounded six more, penetrating the UAE’s vaunted air defences for the first time.

Proxy forces backed by Abu Dhabi had earlier pushed back a Houthi advance towards the government-held city of Marib.

The UN security council on Friday condemned the Houthi attack. “The members of the security council condemned in the strongest terms the heinous terrorist attacks in Abu Dhabi, United Arab Emirates, on Monday, 17 January, as well as in other sites in Saudi Arabia,” the council said. “The members of the security council underlined the need to hold perpetrators, organisers, financiers and sponsors of these reprehensible acts of terrorism accountable and bring them to justice.”

In a separate statement, the council also condemned Friday’s Saudi strikes.

Yemen’s civil war has been a catastrophe for millions of its citizens who have fled their homes, with many close to famine. The UN has estimated the war had killed 377,000 people by the end of 2021, both directly and indirectly through hunger and disease.