No one was injured or threatened in the incident, and the man — a Saudi national, according to a Saudi official — was arrested by members of the National Guard. He is now being interrogated by police.

“An individual with a gun was stopped at the outer security perimeter of the consulate in Dhahran at 6 a.m. and has been detained by Saudi authorities,” a US official said.

The consulate was immediately closed for normal operations as officials began assessing the situation.

“Following this assessment, we will advise the American community and the public as to when the Consulate General will reopen,” an official at the consulate said.

He added that no one was injured or directly threatened in the incident, but that the consulate has decided to close so it can “assess its own security position”.

A State Department official in Washington said an “armed visitor” was arrested at the outer gate of the consulate.

Saudi officials confirmed the incident, saying that the man was “mentally unbalanced”. The Dhahran Academy School, which is also in the same vicinity, was closed as a precautionary measure.

The gunman’s arrest came a week after suspected Al-Qaeda suicide bombers attacked three Riyadh compounds housing mainly foreigners, killing at least 25 people, including seven Americans. Nine suicide bombers carried out the attacks.

Security at all US diplomatic missions in the Kingdom has been stepped up following the Riyadh bombings and a US warning of possible Al-Qaeda attacks in Jeddah.