Three US senators received a classified briefing on Wednesday about an increase in UFO sightings by Navy personnel, Politico reported.

In April, the Pentagon said there had been an increase in reported UFO sightings, with pilots reporting seeing cylindrical objects flying at hypersonic speed off the US East Coast.

The Pentagon in 2017 set up a special program to investigate the increase in UFO sightings.

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Three US senators received a classified briefing about UFOs seen traveling at hypersonic speed by US Navy pilots, congressional and government officials told Politico.

A spokesperson for Sen. Mark Warner, the vice chairman of the Senate Intelligence Committee, confirmed to the outlet that the Virginia Democrat was among those present at the briefing.

"If naval pilots are running into unexplained interference in the air, that's a safety concern Senator Warner believes we need to get to the bottom of," Rachel Cohen, the senator's spokesperson, said in a statement.

In April, the US Navy reported that there had been an increase in the number of sightings of UFOs by its pilots — though it said there was no reason to believe they were extraterrestrial in origin.

Sen. Mark Warner. REUTERS/Aaron P. Bernstein

The Navy said in a statement that there had been "a number of reports of unauthorized and/or unidentified aircraft entering various military-controlled ranges and designated air space in recent years."

"These kinds on incursions can be both a security risk and pose a safety hazard for both Navy and Air Force aviation," it added.

It said it had updated its procedures for personnel to report UFO sightings in response to the incidents.

According to The New York Times, a number of pilots have reported close encounters with unidentified objects that flew close to their aircraft. Pilots described to The Times seeing objects that were cylindrical in shape and performing impossible maneuvers at high speed off the east coast of the US.

In 2017, the Pentagon set up a program to study the increased number of sightings of UFOs traveling at high speeds and performing seemingly strange maneuvers in protected military airspace.

The program was set up following a request by former Democratic Sen. Harry Reid of Nevada.

President Donald Trump in a recent interview with ABC News said he "doesn't particularly" believe in UFOs when asked about the recent sightings by US Navy pilots.