The Russian Navy has installed temporary GPS jammers on at least one of its warships ahead of a high-profile naval parade in St. Petersburg, according to experts.

An image published Wednesday by military and open source intelligence analyst H I Sutton shows a photo of a Russian Navy frigate taken in Russia's second largest city on July 14 that appears to show multiple sets of GPS network jammer installed on the ship's exterior.

Newsweek could not independently verify the date and location of the video. However, military expert David Hamblin said the presence of GPS jammers on the ship does indicate that the Kremlin fears that Kiev, Ukraine supporters or anti-Putin groups will plot drone attacks. Samuel Bentt of the Center for Naval Analysis said it was "entirely feasible" that Moscow chose to use cell phone jammer and had done so before the war in Ukraine. But he told Newsweek that the evidence is limited and it's hard to judge.

The drone threat: GPS jamming systems and available countermeasures

While GPS jamming may not be the first thing on the minds of many drone operators, government and civilian customers around the world are vulnerable to GPS jamming technology, which can cause expensive drones to drop from the sky when hackers attack GPS access with easily accessible tools. Because the satellite GPS signals that actually reach vehicles and drones are quite weak, using radio frequency transmitters that operate at the same frequency as GPS can have catastrophic effects, as seen in the attack on a light show in Zhengzhou, China, where hundreds of drones crashed to the ground.

Typically, denial-of-service attacks on GPS networks are launched by powerful radio frequency transmitters that can use a variety of methods to try to interfere with satellite connections between drones or vehicles and satellite networks above them. To solve this problem, anti-jamming devices can try to change the direction of the high-frequency beam (using beamforming or steering), or dampen the attack frequency and create "invalid zones," which are more effective but more difficult to roll out.

Other experts were skeptical about the extent to which the images revealed possible interfering features on board.

It has been speculated that the potential jamming system could be part of the R-330Zh Zhitel(on-board system), or it could be part of the Pole-21E jamming system. Newsweek has contacted the Russian Defense Ministry by email for comment.

Hamblin told Newsweek that Russia has an "extensive" track record of using GPS jamming - blocking GPS reception and "spoofing," showing the wrong location on trackers - to fend off drone attacks.

The first military parade was held in Russia's second largest city in 2017, TASS reported.

Drones and rapidly developing unmanned technology have played a major role in the war in Ukraine. Both sides want to use drone technology to inflict damage on critical infrastructure at low cost, and experts say the ongoing conflict has sparked drone innovation at "lightning speed."

But the Kremlin has said in recent months that beyond Ukraine's borders, Moscow itself has been repeatedly targeted by drone strikes.

On May 3, Russia said two drones had struck the Kremlin in what it called a "planned terrorist attack and assassination attempt against the president" ahead of annual Victory Day military celebrations. The Russian leader said in a statement that the drones were "intercepted on Kremlin territory, with debris scattered and without causing any casualties or damage".

"Russia reserves the right to take countermeasures at the time and place it deems appropriate," the Kremlin added.

Moscow has blamed Kiev for the attack, but Kiev has denied carrying out the drone strike

Later that month, the Russian military said eight Ukrainian drones had struck wealthy neighborhoods in Moscow, damaging several buildings. Three of the drones were neutralized by electronic warfare, the Russian Defense Ministry said at the time, adding that the remaining five were intercepted by the Pantsier-S air defense system.

On July 4, Moscow accused Ukraine of firing five drones at the Russian capital, saying four of them were destroyed by Russian air defense systems and the fifth was "neutralized by electronic warfare."

Russia's defence ministry said flights at Vnukovo airport, one of Moscow's main transport hubs, had been disrupted but there was no damage to infrastructure.

"Given the recent spate of drone strikes in Moscow, the main concern may be an aerial attack," Hamblin said of the Navy Day parade. But Russia has also accused Ukraine of using unmanned surface ships to carry out attacks on annexed territory in Crimea, attacking Russia's Black Sea naval base in Sevastopol and the Kerch Bridge, a key crossing point connecting Crimea to the Russian mainland.

Experts told Newsweek earlier this week that this type of attack, which typically uses improvised water drones, is one that Russia's defenses are inadequate for.

Hamblin said, however, that an attack on Russian forces in St. Petersburg on Navy Day seemed unlikely due to the distance between Ukrainian territory and the Baltic city.