Saudi Arabia's foreign minister accused the Lebanese militant group Hezbollah on Monday of firing a missile at the capital Riyadh on Saturday, under the orders of Iran. Foreign Minister Adel bin Ahmed told CNN Monday that Saudi Arabia considers the attack an act of war by Iran.

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"It was an Iranian missile, launched by Hezbollah, from territory occupied by the Houthis in Yemen," al-Jubeir told CNN.

A ballistic missile fired at Riyadh from Yemen was intercepted by Saudi air defense on Saturday. State-owned Al Ekhbariya TV reported that the missile was intercepted north of King Khaled International Airport. No casualties were reported.

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Yemen's Iran-backed Houthi rebels had claimed the attack.

"We see this as an act of war," al-Jubeir said. "Iran can not lob missiles at Saudi cities and towns and expect us not to take steps." Al-Jubeir then cited article 51 of the UN Charter, which says a nation can act if an armed attack is made against it.

The Saudi minister said the missile was manufactured in Iran and smuggled in parts into Yemen, where it was assembled and launched with the help of "operatives from the Iranian Revolutionary Guards and Hezbollah."

Saudi Arabia reserves "the right to respond in the appropriate manner at the appropriate time," he said.

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U.S. President Donald Trump also was quick to blame Iran on Sunday. "A shot was just taken by Iran, in my opinion, at Saudi Arabia. And our system knocked it down," Trump said, referring to the Patriot missile batteries Saudi Arabia purchased from the U.S., on Air Force One en route to Tokyo.

The head of Iran’s Revolutionary Guard denied Trump's accusation, calling it as one of the U.S. president’s “slanders."

Mohammad Ali Jafari, who is in charge of Iran's missile program, said: "Mr Trump has said many baseless things and told many lies and frequently, falsely accused Iran and this is one of those slanders," Iran's state news agency IRNA reported.

"We do not have even the possibility to transfer missiles to Yemen. The missiles belong to them and they have increased their range," Jafari added.

The Houthis said in a statement that the missile was launched in response to bombings that have killed civilians. The Houthis have fired a number of missiles across the border in recent years, but this appeared to be the deepest strike yet within Saudi territory.

With reporting by Reuters and the Associated Press