Yemen's Houthi group said on Saturday that it had launched large-scale attacks targeting the Saudi capital Riyadh and Yanbu, a major industrial and energy hub on Saudi Arabia's Red Sea coast, marking a major escalation in the confrontation between the two sides.

In a statement broadcast by Houthi-run al-Masirah TV, Houthi military spokesperson Yahya Sarea said the operations involved "a large number of ballistic and cruise missiles and drones."

Sarea said the first operation targeted what he described as "sensitive targets" in Riyadh, while the second struck a facility belonging to Saudi oil giant Aramco in Yanbu.

"The two operations were successful," Sarea said, claiming that large fires broke out at the targeted sites.

The Houthi statement came after explosions were heard in Riyadh twice on Saturday.

Saudi authorities had earlier issued an aerial threat alert for Riyadh before announcing that the danger had passed, reportedly the first such alert for the Saudi capital since tensions between the Houthi group and Saudi Arabia intensified recently.

In a later statement, the Saudi-led coalition said that its air defenses intercepted and destroyed a Houthi ballistic missile targeting Riyadh and thwarted attacks on Baish, Taif, Farasan and Yanbu. Coalition spokesperson Turki Al-Maliki said the attacks targeted "civilians and civilian objects" and vowed "appropriate measures" to deter further attacks.

Sarea, the Houthi spokesperson, denied that the group deliberately targeted civilians, saying that the attacks against Riyadh were in response to intensified Saudi airstrikes on Houthi-held areas in Yemen.

The spokesperson vowed that the Houthis would continue retaliatory operations under what he called an "escalation for escalation" strategy until Saudi airstrikes cease and restrictions on Yemen are lifted.

The latest escalation comes as the conflict between the Houthis and Saudi Arabia has emerged as a new front in the wider regional war that began with US and Israeli strikes against Iran at the end of February.

Against this backdrop, Tehran has also signaled that it wants the fighting between the Houthis and Saudi Arabia to end while outlining conditions for a possible resumption of stalled negotiations with Washington.

Mohsen Rezaei, secretary of Iran's Supreme National Security Council, told Al Jazeera in an interview that aired on Saturday that Tehran wanted the war between Saudi Arabia and the Houthis to end, adding that he believed Yemenis also wanted a settlement with Saudi Arabia.

Rezaei said Iran had conveyed its conditions to mediators for re-engaging in stalled negotiations with the United States. Among them, he said, were "ending the war on all fronts," the release of frozen Iranian assets and an end to the US naval blockade.

Consultations were continuing with Qatari and Pakistani mediators, Rezaei said, adding that Tehran was awaiting a response from US President Donald Trump.

Iranian reports have referred more broadly to seven conditions communicated to Washington through intermediaries, particularly in connection with the reopening of the Strait of Hormuz. However, the complete official list has not been publicly released.

Meanwhile, the strategic waterway remains a key focus of the broader regional crisis.

On Saturday, US Central Command chief Admiral Brad Cooper said in a video message that the strait's primary transit lanes had been cleared of mines and that Gulf allies had shipped more than one billion barrels of crude through the waterway "in the last couple (of) months."

(With input from agencies)