Saudi Arabia's Crown Prince Mohammed bin Salman has accused Iran of an act of "direct military aggression" by supplying missiles to rebels in Yemen.
This "may be considered an act of war", state media quoted the prince as telling UK Foreign Secretary Boris Johnson in a telephone conversation.
On Saturday, a ballistic missile was intercepted near the Saudi capital.
Iran denies arming the Houthi movement, which has fought a Saudi-led coalition backing Yemen's government since 2015.
Foreign Minister Mohammad Javad Zarif said the prince's claim was "dangerous".
Houthi-aligned media reported that the rebels had fired a Burkan H2 ballistic missile at King Khaled International Airport, which is 850km (530 miles) from the Yemeni border and 11km north-east of Riyadh. Saudi missile defences intercepted the missile in flight, but some fragments fell inside the airport area.
Human Rights Watch said the launch of an indiscriminate missile at a predominantly civilian airport was an apparent war crime.
The official Saudi Press Agency reported on Tuesday that in his telephone call with Prince Mohammed, Mr Johnson had "expressed his condemnation of launching a ballistic missile by Houthi coup militias".
"For his part, the crown prince stressed that the involvement of the Iranian regime in supplying its Houthi militias with missiles is considered a direct military aggression by the Iranian regime and may be considered an act of war against the kingdom," it added.
Mr Zarif condemned Saudi Arabia's "provocative actions" in a telephone call with Mr Johnson later on Tuesday, foreign ministry spokesman Bahram Qassemi said.
"He dismissed false and dangerous claims made by Saudi officials, and said they are against international law and the UN Charter," Mr Qassemi added.