Reuters video and photographs showed a huge pillar of black smoke rising in the area, with the airport highway, main terminal building and other facilities in the foreground.
There was no immediate comment from the Saudi government's media office in response to Reuters questions about the smoke and the overnight alerts.
Saudi civil defence sent the alerts by phone overnight for potential danger in Riyadh and the city of Al-Kharj east of the capital, before issuing an all-clear on Saturday morning. A Reuters journalist in Riyadh's Olaya area heard booms before the all-clear was sent.
Although some alerts had been issued in Riyadh this year after the start of the US-Iran war, these were the first since the escalation began with the Houthis in July.
The Houthis, who control the most populous parts of Yemen and much of the north, have been launching attacks towards Saudi Arabia since declaring a naval blockade against Riyadh in July, with strikes targeting Saudi vessels in the Red Sea.
The attacks have created new threats to global oil supplies, putting at risk the main alternative Red Sea route for Gulf exports while traffic through the Strait of Hormuz remains blockaded.
On Friday, Houthi military spokesperson Yahya Saree said the group had foiled unspecified "criminal attempts" in the Yemeni capital Sanaa, blaming Saudi Arabia and vowing a response.
The group, which seized Yemen's entire Red Sea coast in a lightning advance this month, says the Saudi Air Force has conducted hundreds of airstrikes against it in recent days.
UN Security Council condemns Houthi attacks on Saudi Arabia
The UN Security Council condemned attacks by Yemen's Houthi group on Saudi Arabia, including strikes on civilian and energy infrastructure that injured civilians, among them women and children.
Council members noted that their August 7 statement condemned Houthi missile attacks on the kingdom and assaults on commercial vessels. They reiterated their condemnation of attacks and threats against shipping in the Red Sea and Bab el-Mandeb, stressing the importance of safeguarding vessels and their crews.
The council demanded that the Houthis "immediately cease their military escalation" and attacks affecting civilians and civilian objects.
Members expressed grave concern about reports of civilians killed and injured and noted that at least 125,000 people have been displaced in Yemen since the start of September, according to the UN Office for the Coordination of Humanitarian Affairs. They warned that further escalation would worsen the country's dire humanitarian situation.
They called for full, safe, rapid and unhindered humanitarian access and demanded the unconditional release of detainees, including 73 UN personnel and staff of NGOs, civil society groups and diplomatic missions.
The council further called for practical cooperation with the Yemeni government to prevent the Houthis from acquiring arms, technical assistance, training and financing for military activities. It reminded all member states of their obligations under the targeted arms embargo.
Members expressed solidarity with Saudi Arabia and affirmed its inherent right to self-defence under international law.
They also reaffirmed their commitment to Yemen's unity, sovereignty, independence and territorial integrity, stressing that sustainable peace "cannot be achieved through violence, coercion, or the use of force."
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Noting their support for UN Special Envoy Hans Grundberg in pursuing a negotiated, inclusive, Yemeni-led and Yemeni-owned political settlement, they also urged the parties to engage constructively with UN efforts.
Saudi Arabia has faced missile and drone attacks attributed to the Houthis in recent days amid escalating regional tensions.
Fighting between Yemeni government forces and the Houthis has also intensified since early July. The renewed fighting ended a period of relative calm that had largely held since a UN-brokered truce took effect in April 2022.