Yemen's Huthi rebels were expelled from a key battleground district by UAE-trained Giants Brigade fighters, the militia said Tuesday, a day after the insurgents' latest missile attack on Abu Dhabi.

The Iran-backed Huthis lost Harib district south of Marib, the government's last northern stronghold which they have been fighting to seize for months.

The Giants Brigade said "hundreds were killed and wounded on both sides" in battles that lasted for more than two weeks and also secured the neighbouring governorate of Shabwa. There was no immediate comment from the Huthis.

"We thank the Arab coalition for their support for our operations in Shabwa, which were crowned with complete success," the Giants Brigade said in a statement, referring to a Saudi-led military alliance.

The clashes are part of a major escalation in the seven-year war after the Huthis, following a series of territorial defeats, launched a deadly drone-and-missile attack on the UAE last week.

The Saudi-led pro-government coalition that includes the UAE hit back with a series of air strikes, one of which killed at least three children and plunged Yemen into a four-day internet outage.

Fighters of the UAE-trained Giants Brigade patrol at the Harib junction, Bayhan district, in Yemen's Shabwa governorate, on January 19, 2022 Fighters of the UAE-trained Giants Brigade patrol at the Harib junction, Bayhan district, in Yemen's Shabwa governorate, on January 19, 2022 Photo: AFP / Saleh Al-OBEIDI

Internet services were restored early on Tuesday, a web monitor and AFP correspondents said.

In rebel-held Saada last Friday, an attack on a prison left at least 70 people dead and wounded more than 100, according to Doctors Without Borders (MSF).

The coalition denied being behind the prison attack, which the Huthis said had killed 91 people and injured more than 200, as they lined up the bodies covered in white sheets along the ground on Tuesday.

On Monday, the rebels renewed their attack on Abu Dhabi when two ballistic missiles were intercepted over the city, scattering debris.

US forces based at the capital's Al-Dhafra air base fired Patriot missiles to help repel the attack, while some of them also scrambled to bunkers, US officials said.

Onlookers gather as Yemenis pray during a mass funeral in rebel-held Saada for those killed in an attack on a prison, which the Huthis said claimed 91 lives and the Saudi-led coalition denied striking Onlookers gather as Yemenis pray during a mass funeral in rebel-held Saada for those killed in an attack on a prison, which the Huthis said claimed 91 lives and the Saudi-led coalition denied striking Photo: AFP / STR

The UAE, which pulled most of its troops out of Yemen in 2019 but maintains support and training for pro-government forces, warned of a "thorough and comprehensive response" to the cross-border attack.

"The UAE reserves the right to respond against these terrorist attacks and such blatant criminal escalation," a foreign ministry statement said, adding that the Huthis had targeted "civilian areas".

Two people were injured in southern Saudi Arabia by further rebel missile attacks on Monday.

US State Department spokesman Ned Price called the Huthi attacks and coalition air strikes "a troubling escalation".

US National Security Adviser Jake Sullivan also met with the UAE and Saudi ambassadors to Washington to "discuss ongoing Huthi attacks against civilian targets that have resulted in civilian casualties in both countries", the White House said Monday.

Arms sales from the United States, as well as Britain and France, back the Saudi-led coalition.

Rights groups have long criticised the coalition for civilian casualties in its aerial bombardments.

According to the Yemen Data Project, an independent tracker, there have been almost 9,000 civilian casualties from coalition air raids since 2015.

Latest developments have sent regional tensions soaring and further complicated the Yemen conflict that is being fought on several fronts.

More than 150,000 people have been directly killed by fighting and millions displaced in the impoverished country, according to the United Nations which calls it the world's worst humanitarian crisis.