The Saudi-led coalition on Sunday accused Iran and Hezbollah of helping Yemen's Huthi rebels to launch missiles and drones at the kingdom, where two people were killed.
Since the coalition intervened almost seven years ago to support Yemen's government, Saudi Arabia has regularly accused Iran of supplying the Huthis with weapons and Hezbollah of training the insurgents.
Tehran denies the charges. Lebanon's Iran-backed Shiite militant movement Hezbollah has previously denied sending fighters or weapons to Yemen.
The latest Saudi accusation came as the coalition intensified an aerial bombing campaign against the Iran-backed Huthis in retaliation for deadly attacks on the kingdom.
Coalition spokesman Turki al-Malki told a news conference the Huthis were "militarising" Sanaa airport and using it as a "main centre for launching ballistic missiles and drones" towards the kingdom.
Malki showed reporters a video clip which he said depicted "the headquarters of Iranian and Hezbollah experts at the airport" where, he alleged, "Hezbollah is training the Huthis to booby-trap and use drones".
Malki showed other clips which he said depicted a Hezbollah member placing explosives in a drone, and a man he identified as a Hezbollah official telling Huthi members "we must strengthen our ranks".
The footage could not be independently verified.
The Arab military coalition led by Riyadh intervened in Yemen in 2015 to back the internationally recognised government, a year after the Huthis overran the capital Sanaa.
Since then, tens of thousands of people have been killed, in what the United Nations has described as the world's worst humanitarian crisis.
The Huthis come from the minority Zaidi Shiite sect of Islam and have their traditional stronghold in Yemen's mountainous north.
Between 2004 and 2010, they fought six wars against Yemen's then-government and battled Saudi Arabia in 2009-2010 after storming over the border.
The deaths of two people overnight Friday from a rebel missile strike on the Saudi city of Jazan were the first such deaths in the kingdom in three years.
- Escalation -
On Sunday, Malki said the international community must "stop hostile acts by this terrorist organisation," a reference to Hezbollah.
Since January 2018 the Huthis have launched 430 ballistic missiles and 850 drones towards Saudi Arabia, he said.
Sunday evening the coalition announced it had made new strikes near an air force academy in Sanaa to prevent weapons from being moved.
Earlier Sunday the coalition said it had struck a Huthi rebel camp in Sanaa, destroying weapons warehouses.
On Saturday, the coalition launched what it called a "large-scale" military operation against the Huthis after the rebel missile strike that hit Jazan.
The coalition raids left three civilians dead, including a child and a woman, Yemeni medics told AFP.
Rights groups have criticised the coalition for civilian casualties in its years-long aerial bombardment.
The coalition maintains its operations are carried out in accordance with international humanitarian law, repeatedly urging the Huthis against using civilians as human shields.
Malki also accused Iran's ambassador to Sanaa, who died of Covid-19 last week after his evacuation from Yemen, of "leading the planning of military operations in Marib" -- the Yemeni government's last stronghold in the north.
The Huthis warned in a statement that they will "face escalation with escalation".
- 'Barbaric attack' -
World powers and the kingdom's Gulf Arab allies condemned the rebels' deadly strike on Saudi Arabia.
"Huthi attacks are perpetuating the conflict, prolonging the suffering of the Yemeni people, and endangering the Saudi people alongside more than 70,000 US citizens residing in Saudi Arabia," Washington's embassy to Riyadh said in a statement.
Ludovic Pouille, the French ambassador to Riyadh, on Twitter offered condolences to families of victims in the "barbaric Huthi attack".
The coalition has intensified its air strikes on Sanaa, including last week on what it called "military targets" at the airport.
United Nations aid flights were interrupted as a result.
The insurgents often launch missiles and drones into Saudi Arabia aimed at its airports and oil infrastructure.
The UN's World Food Programme said it has been "forced" to cut aid to Yemen due to lack of funds, and warned of a surge in hunger.