Russia's Black Sea Fleet has taken hits, but intel says military leaders may be more worried about an airbase attack near Moscow

• Ukraine has relentlessly targeted the Black Sea Fleet based in occupied Crimea in recent days.
• But Western intel says Russia may be more worried about recent explosions at a Moscow-area airbase.

Ukrainian forces have relentlessly targeted Russia's Black Sea Fleet over the last two weeks, but a recent attack at an airbase closer to home may have Moscow's military leadership more concerned.

Britain's defense ministry wrote in a Friday intelligence update that both Russia and Ukraine have experienced "unusually intense attacks deep behind their lines" over the past few days, noting recent attacks on both the Black Sea Fleet in occupied Crimea and the Chkalovsky Air Base, which is located just outside Moscow.

The airfield "hosts specialist military aircraft as well as VIP transport for Russian leaders," the UK said, making it a "sensitive" location for Russia.

Ukraine claimed earlier this week that unknown saboteurs blew up several military aircraft at Chkalovsky. A Ilyushin Il-20 (referred to by NATO as a "Coot") special mission aircraft — a "valuable" asset that can "undertake missions which include electronic intelligence collection — was reportedly damaged in the explosions, Britain's defense ministry said.

In addition to that aircraft, the Ukrainian Main Directorate of Intelligence, an arm of the country's defense ministry (also known as the HUR), said the sabotage effort also damaged a Mil Mi-28 attack helicopter and a Antonov An-148 passenger aircraft. Ukraine claimed the attack caused "hysteria" among Moscow's military command given the base is also said to be home to high-profile platforms like reconnaissance aircraft and Russia's so-called "doomsday" planes.

The Monday attack marked the latest in a string of assaults specifically targeting Russian airfields and airbases. These attacks, many of which have taken place within Russia's internationally recognized borders and hundreds of miles from current fighting in Ukraine, have exposed serious shortcomings in Moscow's force protection and domestic security capabilities.

But Russia is also taking hits elsewhere. Ukraine's forces have launched several missile strikes on assets belonging to Russia's Black Sea Fleet, which is based in the occupied Crimean peninsula. On Wednesday, Kyiv said it hit a command post near the port of Sevastopol, and Russia's defense ministry admitted on Friday that the fleet's headquarters in the city was damaged by Ukrainian missiles. These attacks came just over a week after Ukraine launched a massive cruise missile strike on a Russian shipyard at Sevastopol, damaging the facility and two warfighting vessels.

Still, Britain's defense ministry said in its intelligence update that even though the Black Sea Fleet has been "heavily targeted" this week, the explosions at Chkalovsky "are likely to be of most strategic concern to Russian leaders" because the airbase is so strategic for the Kremlin and hosts prized aircraft.

These long-range strikes have not been one-sided, though, as Russia has continues to attack Ukraine's cities and civilians with missiles and drones. Britain's defense ministry attributed the increase in deep strikes to a slow-moving battlefield, where Ukrainian forces continue to make steady territorial gains in their grinding counteroffensive.

"Russia has launched long-range strikes at targets across Ukraine repeatedly over the last week," Britain's defense ministry said. "This unusual intensity is likely partially in response to the incidents in Russia and Crimea. With the ground battle relatively static, each side is seeking advantage by striking through their adversary's strategic depth."

While the lines are largely static, Kyiv's forces on Thursday to have achieved something of a breakthrough along a portion of the front lines. Its forces managed to advance heavy Western armor beyond two formidable layers of Russia's defensive lines in the southern Zaporizhzhia region — a notable development that could pave the way for bringing forward more firepower.