Unidentified drones flying over US military bases in the UK are not likely to be operated by hobbyists.

Nearly a week ago, unidentified drones were sighted over joint U.S.-U.K. military bases in the UK.

Since Wednesday, November 20, four U.S. military bases in the U.K. that house American F-15 Strike Eagle and F-35 fighter jets have been targeted by "swarms of small drones."

Military officials are concerned about a suspected coordinated attempt to test security measures at RAF Lakenheath, RAF Mildenhall, RAF Feltwell, and RAF Fairford in England.

Around 60 U.K. military personnel have been deployed to safeguard the bases under threat from numerous drone attacks.

According to a senior U.S. official, the drones in question do not resemble hobbyist drones. Instead, they are described as small quadcopters and octocopters that are more advanced than typical consumer models.

Earlier Tuesday, Maj. Gen. Pat Ryder, the Pentagon press secretary, stated that none of the drone incursions have affected the base residents, facilities, or U.S. assets on the bases.

Ryder stated that we always have the right to defend ourselves if we perceive something as a threat.

The coordinated nature of the drone attacks suggests an aggressive state actor, with the origin of the drones remaining unknown. This occurred one day after Ukraine used long-range American ATACMs to target Russia, following President Biden's decision to lift restrictions on the use of longer-range missiles.

After President Putin's statement, Russia has the right to attack countries that permit their weapons to be used against them.

The Defense Ministry in the U.K. is collaborating with U.S. and local law enforcement to investigate the activities of these drones and determine if a foreign enemy is involved.

"The number of systems has varied, and they have come in different sizes and configurations, according to the U.S. Air Forces Europe. "Our units remain vigilant and are collaborating with host-nation authorities and mission partners to safeguard the well-being of base personnel, facilities, and assets," the statement added."

A month after Fox reported that surveillance drones flew for 17 days near Langley Air Force Base in Virginia last December, the incursion of drones poses a similar challenge to base commanders.

The 48th Fighter Wing, the foundation of the U.S. Air Force's combat capability in Europe, is located at Lakenheath. The 100th Air Refueling Wing, which hosts the U.S. Air Force's largest refueling aircraft, is located at Mildenhall. Feltwell serves as a hub for housing, schools, and other services. Fairford is home to the 501st Combat Support Wing Headquarters and the 420th Air Base Squadron.

The Associated Press contributed to this report.