Saudi Arabia issued air-raid alerts for Riyadh, Jeddah, Yanbu and several other cities overnight as Iranian-backed Houthis stepped up missile and drone attacks on the kingdom. It was the first warning for the Saudi capital since the rebels reignited the decade-long war in July, shattering a four-year truce. All-clear messages followed shortly after, and no damage was reported, though residents in Riyadh heard a loud boom.

Over the past 10 days the Houthis have escalated strikes while advancing south along Yemen's Red Sea coast to tighten control of the Bab al-Mandeb Strait, a critical international waterway. Saudi authorities said dozens have been wounded this month and some southern oil operations have been halted. A separate drone attack from Iraq, where Iranian-aligned Shia militias and Tehran's Revolutionary Guards operate, forced Saudi Aramco to close a pipeline used to ship crude from the east to the Red Sea port of Yanbu.

The attacks have pushed oil prices to their highest levels since mid-May. Saudi Arabia intervened in Yemen's civil war in 2015 to lead an Arab coalition against the Houthis after they seized Sana'a and ousted the internationally recognised government. A 2022 truce largely held until the Houthis declared a blockade on Saudi ports and attacked Saudi tankers in July.

Analysts say the rebels, who receive arms and technology from Iran, have developed more advanced weaponry. They demand Riyadh pay salaries in Houthi-controlled areas, grant access to Yemen's oil revenues, and allow free movement at rebel-held ports and airports. The escalation also bolsters Iran's pressure on global energy prices in its confrontation with the US.

The Houthis accuse Saudi Arabia of launching more than 300 air strikes in Yemen over the past week as Saudi-backed Yemeni factions try to reverse the rebel offensive along the Red Sea coast.