Pakistan and Turkey meanwhile pledged to deploy troops to Saudi Arabia under a new mutual defense pact following weeks of Houthi attacks, as Riyadh and its Yemeni government allies began an ambitious push aimed at retaking all territory held by the group.

The Yemeni military said it carried out more than 1,000 strikes and began an offensive against the Houthi-held capital, Sanaa, while the Saudi-led coalition supporting the internationally recognized government said 100 warplanes flew sorties at dawn.

Turki Al-Malki, spokesman for the Saudi-led coalition said on X that its naval forces had hit "military targets” belonging to the Houthis in Hodeida on the Red Sea coast.

They "destroyed weapons depots, facilities storing booby-trapped boats and naval mines" and had "thwarted a planned attack" targeting waterways in the southern Red Sea, he said.

Loud explosions rattled Riyadh on Monday evening as the fighting escalated, and a Houthi spokesman said the group had hit the Saudi capital's King Khalid International Airport as well as an Aramco refinery and other targets in the kingdom's south.

The government announced on Sunday the lofty goal of retaking all Houthi territory -- home to most of Yemen's population, and much of it held for more than a decade.

Last month the Iran-backed group seized swathes of coastline along the Red Sea and Bab al-Mandab Strait, a chokepoint for oil and cargo shipping, in Yemen's deadliest fighting in years.

The Houthis have also been attacking neighboring Saudi Arabia since Yemen's civil war flared back to life, and have declared a maritime blockade on its ships.

On Monday, representatives of Saudi Arabia, Pakistan and Turkey held an emergency meeting in Riyadh under the auspices of a joint defense agreement signed in August committing them to come to each other's aid in the event of any attack.

They also agreed "to take the necessary measures to provide the agreed military forces and capabilities and ensure their rapid deployment in the Kingdom".

The statement did not specify what sort of role the troops would fill once in Saudi Arabia.

A spokesman for UN Secretary-General Antonio Guterres said he was "deeply concerned by the sharp escalation in fighting", and condemned "the continued Houthi cross-border attacks" on Saudi Arabia".

Global oil system 'straining'

Houthi attacks have also targeted Saudi oil infrastructure, as well as its tankers in the Red Sea.

A source in the Saudi energy sector told AFP that an attack Sunday had again halted pumping by the East-West pipeline to the Red Sea, a key conduit for the kingdom's exports since Iran blockaded the Strait of Hormuz at the start of the wider Middle East war.

Crude prices had already been soaring as a result of the Middle East war, before the Houthis began targeting the world's largest oil exporter.

Saudi Aramco chief executive Amin Nasser warned on Monday that global oil stockpiles were "scarily thin" owing to the war.

"The system is already straining," Nasser told the Energy Intelligence Forum in London.

Mokha fighting

Yemeni military sources said Monday that pro-government forces had cut off the only supply route to the Houthi-held city of Mocha, but stopped short of confirming an official announcement of the port's recapture.

While the war in Yemen predates the broader Middle East war that began with US-Israeli strikes on Iran, it has become its most active front in recent weeks. According to UN figures, the fighting has displaced more than 184,000 people.

Yemen's civil war began broke out in 2014, with the Saudis intervening the following March, but fighting was paused by a 2022 ceasefire that held until July of this year.

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