Iran-backed Houthi rebels struck a residential area in Yemen’s third-largest city on Tuesday, killing two teenage girls and renewed attention to the dangers faced by civilians in Taiz, which has been under attack and siege during the country’s escalating conflict.

The Houthis have largely encircled Taiz and cut off most supply routes from government-held areas, putting civilians at “grave risk,” U.N. human rights chief Volker Türk said Tuesday. The U.N. says the siege has sent prices soaring, leaving many residents without food and other necessities.

Also on Tuesday, a senior Yemeni government official said the death toll from a Houthi missile strike a day earlier on a government military camp rose to 73 people, making it the deadliest strike since the resurgence of the conflict over the summer.

The conflict has only intensified since forces from the internationally recognized government and Saudi-led coalition launched airstrikes on Houthi-held Sanaa International Airport in July, shattering a 2022 ceasefire deal that largely stopped fighting in the country’s civil war.

Yemen has become a widening front in the Iran war that began in February — and the Houthis have increasingly launched attacks on Saudi Arabia because it supports Yemen’s internationally recognized government. Britain said Tuesday it is expanding its military support for Saudi Arabia to include “defensive” air patrols by Royal Air Force jets.

UN warns of humanitarian crisis In the deadly strike on Taiz, six other people were wounded and several buildings were damaged, local authorities said.

The Houthis have besieged Taiz as part of their monthslong offensive against Yemeni government forces, repeatedly targeting it with missiles and artillery.

Get daily National news“Humanitarian aid must be immediately allowed to enter the city and its passage must be facilitated. Civilians wishing to leave must be allowed to do so freely and safely,” Türk, the human rights chief, said.

He urged the Houthis and Saudi-backed government forces to avoid using explosive weapons in areas where they could hit civilians and civilian infrastructure.

UK deploys RAF jets to defend Saudi Arabia The Houthis have also fired missiles and drones at Saudi Arabia, which has struggled to counter the attacks, even with far superior U.S.-supplied arms.

Tom Barrack, the U.S. envoy to Syria and Iraq, told the Global Security Forum in Doha, Qatar, that while he understood that “Saudi Arabia is in a very difficult position,” the United States was not prepared to send troops to help.

“I think the president has been clear that he supports Saudi Arabia, and the backing that they need logistically we’ll supply, but America getting involved in a ground kinetic battle somewhere else seems fruitless,” said Barrack, who is also the U.S. ambassador to Turkey.

U.K. Defense Secretary Wes Streeting said the British government would expand its support to Saudi Arabia to include defensive patrols by RAF jets to protect Saudi cities from attacks but would not strike Houthi targets.

It means the British planes would attack missiles or drones in the air, but Streeting said they would not strike Houthi targets on the ground. Britain had already offered to help with in-air refueling of Saudi planes.

The Egyptian government also will deploy air defense systems and aircraft to help repel missiles and drones fired toward Saudi Arabia but won’t deploy ground troops to Yemen, according to a regional official who was briefed on the matter. The official spoke on condition of anonymity because he wasn’t authorized to speak to reporters.

Houthis fired ballistic missiles The Monday ballistic-missile strike on the al-Alam military camp hit while recruits were lining up in formation for a training session.

More than 200 recruits were wounded in the attack. The recruits were all aged between 18 and 20, Shabwa governor Awad Ibn al-Wazir told AP. They were being trained to provide security in the province and not for combat operations, he said.

“This had nothing to do with front lines,” he said. “They had not attacked anyone or advanced against anything. It was only to protect the security of their province.”The Shabwa provincial government said in a statement Monday that the Houthis fired three ballistic missiles on the camp. The Houthis claimed the attack, saying they had killed and wounded dozens but did not provide further details.

The camp, previously used by a militia backed by the United Arab Emirates, is in the Jardan district, north of the provincial capital, Ataq. It sits on a crucial supply route to the government-controlled province of Marib.

Shabwa, Marib and neighboring Hadramawt province form what has been dubbed the Yemeni government’s “triangle of power,” a strategic area that contains the country’s oil and gas production facilities.

Saudi authorities issued an attack warning for the capital area late Tuesday morning. An explosion was then heard in northern Riyadh, where King Khalid International Airport is located. Repeated Houthi attacks this month have forced the airport to suspend operations. The all-clear was given shortly afterward, and Saudi Arabia said it had intercepted a ballistic missile fired by the Houthis.

Yemen plunged into civil war in 2014, when the Houthis seized Sanaa and much of northern Yemen and forced the government into exile. A Saudi-led coalition intervened the following year in an attempt to restore the government to power. The conflict killed more than 150,000 people and created one of the world’s worst humanitarian disasters.