Monday, Ukraine attacked two airfields deep within Russia, sparking a bombardment from Moscow that targeted civilian houses and infrastructure and increasing the threat of a further escalation in the nine-month conflict.

Monday, the Russian Ministry of Defense reported that Ukrainian drones infiltrated Russian airspace and attacked two air bases in the south-central region of the country, located in Ryazan and Saratov.

Russia reported that three personnel were killed, four were injured, and two jets were damaged in the strike.

One of the airfields, the Engels air station outside of Saratov, is home to a squadron of bombers equipped with nuclear weapons.

"To disable Russian long-range aircraft, the Kyiv government attempted to strike military airfields Dyagilevo in the Ryazan region and Engels in the Saratov region using Soviet-made unmanned jet aircraft," the Russian defense ministry claimed.

The New York Times claimed on Monday that an unnamed senior Ukrainian official confirmed Kyiv's involvement in the attack. Officially, however, Ukraine refrained from claiming credit for the strike.

Mykhailo Podolyak, an advisor to Zelensky, said in a tweet, "If something is launched into the airspace of another nation, unidentified flying objects will eventually return to their point of origin."

If verified to be a Ukrainian operation, the attack would be the most audacious Ukrainian incursion into Russian territory since the Russian invasion in February.

Since the beginning of the war, Kyiv has denied any activity beyond the border, while Russia has claimed many instances of Ukrainian air strikes on Russian staging areas several miles from the border.

However, the cities of Ryazan and Saratov have located hundreds of miles from the Ukrainian border and are also further east than Moscow.

Russia conducted a huge missile strike on Monday, firing 70 missiles targeting Ukrainian cities and infrastructure as a form of retribution.

Kyiv asserted that 60 of the missiles were successfully intercepted, but Ukrainian President Volodymyr Zelensky stated that four civilians were killed in the attack.

There were reports of missile strikes in Cherkasy, Krivyi Rih, and Odesa. Water, power, and central heating were disrupted throughout much of the historic port city of Odessa in the south.

The assaults are part of a systematic Russian operation to target Ukraine's electrical grid in advance of the winter months, in an attempt to break Ukraine's resistance.

However, in his nightly address on Monday, Zelensky praised Ukrainian air defense for intercepting the vast majority of incoming attacks.

"Every Russian missile shot down is tangible evidence that terror can be destroyed," he declared.