Residents in Saudi Arabia's Riyadh have been given the all-clear after air raid alerts were issued and explosions were reported in the capital.

It was the first time alerts have been issued in Riyadh since the Houthis increased their attacks and declared a "maritime embargo" on the Saudis in July.

The Saudi Civil Defence sent alerts for the capital and several other regions late on Friday night and Saturday morning (local time) as the Kingdom's conflict with the Iran-backed Houthis continued to escalate.

Journalists from Reuters and AFP reported hearing explosions in the capital, but authorities have since said the danger has passed. Residents were urged to avoid gathering in crowds.

The Houthis recently seized control of the strategic port city of Mokha and Perim Island, a gateway to a key shipping route used by the Gulf state to export to Asia and Europe.

The Iran-backed group's military spokesman said the naval blockade was in retaliation for a Saudi blockade of ports and airports in Houthi-controlled north-western Yemen.

Saudi vessels have relied on that stretch of the Red Sea for oil exports since the US and Israel's war with Iran effectively closed the Strait of Hormuz.

Last week, the Houthis attacked several Saudi oil facilities with drones and missiles, causing fires which led to operations being temporarily halted.

The attacks on Saudi oil assets have directly impacted global energy markets and the price of petrol and diesel in many countries has sharply risen in recent weeks, compounding already elevated costs caused by the blockades of the Strait of Hormuz.

Saudi Crown Prince Mohammed bin Salman, the country's de facto ruler, has personally asked US President Donald Trump to take military action against the Houthis, two sources familiar with the matter told CBS News, the BBC's US media partner.

Trump has so far declined to involve the US military directly, offering instead to assist with intelligence and targeting support, the sources said.

A senior Trump administration official told the BBC: "We are in continuous dialogue with Saudi Arabia and the Republic of Yemen government regarding regional stability."

Earlier this week, Houthi military spokesman Yahya Sarea said the Houthis had launched drones and missiles at Saudi Arabia in retaliation for more than 450 Saudi air strikes on their territory over the past week.

The United Nations Security Council held an emergency meeting on Tuesday, during which both Yemen's government and Saudi Arabia called for more decisive action against the Houthis, who they accused of choking the Bab al-Mandab Strait as a way of applying economic pressure.

Council members agreed that freedom of navigation in the Red Sea must be maintained to prevent disruption to global supply chains.

Yemen has been devastated by a civil war that began in 2014, when the Houthis ousted the government from the capital, Sanaa. The conflict escalated in 2015, after the Saudi-led coalition of Arab states intervened in an attempt to restore the government's rule.

The fighting has reportedly left more than 150,000 people dead and triggered one of the world's worst humanitarian crises, with more than 22 million people in need of some form of aid, according to the UN.