Three Russian military personnel were killed by falling wreckage from a Ukrainian drone that was shot down over a bomber airbase in southern Russia Monday, the second time the key military site has been targeted this month, exposing weaknesses in its defenses.

Moscow confirmed it had shot the drone down causing it to crash at the Engels air base in the Saratov region deep within Russia, leaving three service members dead.

Saratov Governor Roman Busargin expressed his condolences to the victims’ loved ones.

The base — the main bomber airfield that Kyiv says Moscow has used in recent months to attack and disable much of Ukraine’s civilian infrastructure — is more than 400 miles east of the Ukrainian border. 
The strategic facility is home to Tu-95 and Tu-160 planes that are designed to launch nuclear-capable missiles.

Monday’s incident comes three weeks after the first suspected Ukrainian drone attack on the Engels airbase, which exposed what was widely described at the time as a humiliating gap in Russia’s air defenses. The latest attack suggests Moscow has yet to beef up security at its military installations.

Russia’s Ministry of Defense said in a statement no planes were damaged, but independent Russian and Ukrainian social media accounts claimed that several aircraft had been destroyed.

In keeping with the Kyiv government’s long-standing practice of not confirming cross-border attacks but welcoming their results, Ukrainian air force spokesperson Yurii Ihnat didn’t directly acknowledge his country’s involvement in the drone attack but said in an interview: “These are the consequences of Russian aggression.”

He added: “If the Russians thought that the war wouldn’t affect them deep behind their lines, they were deeply mistaken.”

Russia has suffered numerous cross-border attacks since the outbreak of the war on Feb. 24 on its main territory, as well as on the Crimean Peninsula, which it illegally annexed in 2014.

The incidents have outraged Russian military bloggers who say they show weaknesses in the country’s air defenses and security systems in general.

On Dec. 5, unprecedented drone strikes on Engels and the Dyagilevo base in the Ryazan region in western Russia killed a total of three servicemen and wounded four others.

Russia retaliated for the humiliation by launching a massive missile barrage in Ukraine that struck homes and buildings and killed civilians.

In another cross-border incident that couldn’t be independently confirmed, Russia’s Tass news agency reported Monday that the country’s security forces had killed four Ukrainian saboteurs attempting to enter the Bryansk region from Ukraine.

The report claimed the infiltrators carried explosive materials and German-made guns when they were caught Sunday.

With Post wires