Yemen's Houthis said they targeted Saudi Arabia's biggest oil refinery with a ballistic missile on Tuesday, as blasts shook the capital of the world's top crude exporter.
Saudi Arabia, the Middle East's largest economy, has suffered weeks of strikes from the Iran-backed Houthis against oil and civilian sites including Riyadh's international airport.
"The Yemeni Armed Forces were able to target the Ras Tanura refinery in the Eastern Province with a ballistic missile," Houthi military spokesman Yahya Saree posted on X, saying the strike caused "massive fires".
The Saudi-led coalition fighting the Houthis earlier said it had shot down three missiles fired by the group towards the Eastern Province.
A resident in the city of Al Khobar, south of the Ras Tanura complex, told AFP he heard explosions around dawn and received a text message alert.
"We got the alert on the mobile and then heard a very loud bang," the resident said.
Maritime security agency Vanguard said a fire was reported in the Ras Tanura area in the early hours of Tuesday after an attack.
"The fire has reportedly been contained, while the extent of damage and any impact on oil-loading operations remain unclear at current," Vanguard said.
The Ras Tanura facility along Saudi Arabia's Gulf coast is home to one of the largest refineries in the Middle East and a cornerstone of the kingdom's energy sector.
The complex has a capacity of 550,000 barrels per day. It has been repeatedly targeted by strikes blamed on Iran, including a drone attack in early March that forced a partial shutdown of the refinery.
Meanwhile a series of explosions echoed across the capital, Riyadh, shaking office windows in the city centre. A text message alert warned residents to seek shelter.
The Saudi-led coalition fighting the Houthis said it intercepted two ballistic missiles that were fired at Riyadh.
Egypt 'declared war'
Earlier, a Houthi official said the Egyptian parliament's decision to authorise defensive military support for Saudi Arabia amounted to a declaration of war.
Egypt's parliament authorised the measure on Monday, following a request from Egyptian President Abdel Fattah al-Sisi.
"It is truly remarkable that while these people go to discuss what they call 'peace in the region', Egypt and its parliament declare support for the so-called defence of the Kingdom of Saudi Arabia, and in doing so, declare war against the Republic of Yemen," said Mohammed Ali al-Houthi, a member of the Houthis' political bureau, in a Telegram post.
It was not clear exactly what support was on offer from Egypt, which has the Arab world's largest military.
Al-Houthi's statement also pointed to Monday's visit to Tehran by the Saudi defence minister, Pakistan's army chief and Turkey's intelligence chief, in a bid to de-escalate tensions in the US-Israeli war on Iran.
Riyadh, Ankara and Islamabad recently signed a NATO-style defence pact in Mecca, pledging to consider an attack on one country as an attack on all three.
Turkey and Pakistan have not announced any strikes on the Houthis during the group's weeks of attacks on Saudi Arabia.
'Not afraid of any alliance'
The Houthis said the group was "not afraid of any alliance that may be formed".
Yemen's largely dormant conflict reignited in July, further destabilising the region months into the Middle East war between the United States and Iran.
The Houthis declared a maritime blockade of Saudi Arabia and began hitting its ships, territory and oil facilities, before seizing swathes of Red Sea coastline in a major offensive in September.
The Houthis have in turn reported frequent Saudi strikes targeting areas under their control.
This month the Houthis ramped up attacks on Saudi Arabia, forcing the cancellation of flagship events and shutting down Riyadh's airport for two weeks.
The Houthis' war with the Saudi-led coalition began in 2015, months after they ousted the internationally recognised government from the capital Sanaa in September 2014.