WASHINGTON - Nearly 175 Saudi Arabian military aviation students have been grounded as part of a "safety stand-down" after a Saudi Air Force lieutenant shot and killed three people last week at a U.S. Navy base in Florida, U.S. officials told Reuters on Tuesday.

The FBI has said U.S. investigators believe Saudi Air Force Second Lieutenant Mohammed Saeed Alshamrani, 21, acted alone when he attacked a U.S. Navy base in Pensacola, Florida on Friday, before he was fatally shot by a deputy sheriff.

The shootings have again raised questions about the U.S. military relationship with Saudi Arabia, which has come under heightened scrutiny in Congress over the war in Yemen and Saudi Arabia's killing of Washington Post columnist Jamal Khashoggi last year.

Still, U.S. military leaders have sought to portray this as a localized issue which would not affect the overall U.S.-Saudi relationship.

"A safety stand-down and operational pause commenced Monday for Saudi Arabian aviation students," said Lieutenant Andriana Genualdi, a Navy spokeswoman.

Saudi Arabia Defense Attache Major General Fawaz Al Fawaz, his embassy staff and other officials arrive to meet with the Saudi students who remain restricted to the Naval Air Station (NAS) Pensacola base by their Saudi commanding officer, in Pensacola, Fla, on Dec. 9, 2019. FBI Jacksonville / Reuters

Another U.S. official said the grounding was to help Saudi students prepare to eventually restart their training and similar procedures would have been taken if such an incident took place in a U.S. military squadron.

Genualdi said the grounding included three different military facilities: Naval Air Station Pensacola, Naval Air Station Whiting Field and Naval Air Station Mayport, all in Florida.

She added that while it was unclear when the Saudi students would be allowed to fly again, their classroom training was expected to resume soon. She added that aviation training had resumed for students from other countries.

There are currently about 850 Saudi students in the United States for military training.

Alshamrani was on the base as part of a U.S. Navy training program designed to foster links with foreign allies. He had started training in the United States in 2017 and had been in the Pensacola area for the past 18 months, authorities said.

A group that tracks online extremism has said Alshamrani appeared to have posted criticism of U.S. wars in predominantly Muslim countries and quoted slain al Qaeda leader Osama bin Laden on Twitter hours before the shooting spree.

The attack comes as President Donald Trump's administration has maintained warm ties with Riyadh amid high tensions with Middle East rival Iran.

U.S. Defense Secretary Mark Esper has dismissed suggestions that the shootings might make him more reluctant about new U.S. deployments to Saudi Arabia, which were announced in October and first reported by Reuters.

"Saudi Arabia is a longstanding partner of ours in the region. We share mutual security interests," Esper said over the weekend.

Esper said he had instructed the armed forces to review both security at military bases and screening for foreign soldiers who come to the United States for training after the shooting.

In the wake of the shootings, the U.S. Northern Command immediately ordered all military installations to review force protection measures and to increase "random security measures."

A Northern Command spokesman said local commanders in the United States also had the authority to "add further countermeasures as needed," without elaborating as to which, if any, bases did so.