Ukrainian president Volodymyr Zelensky justified military attacks on Russian territory, calling it "fair" and "inevitable."
"Ukraine is getting stronger. Gradually, the war is returning to the territory of Russia, to its symbolic centers and military bases, and this is an inevitable, natural, and absolutely fair process," Zelensky said in a televised address on Sunday.
The comments came the same day that Russian officials say three Ukrainian drones were downed in Moscow, the latest instance of Ukraine bringing the fight into Russia proper. Two office buildings just miles from the Kremlin were damaged in the attack.
"Russian aggression has gone bankrupt on the battlefield," Zelensky said. "Today is the 522nd day of the so-called ‘special military operation,’ which the Russian leadership expected to last for a week or two."
The drone attack follows the May 3 incident where two explosive drones were shot down over the Kremlin. Ukraine denied responsibility for the act.
The comments also follow escalating tensions between Russia and the United States.
A Russian fighter jet last week shot flares at a U.S. drone over Syria, causing damage to its propellers.
In March, a Russian fighter jet again damaged the propellers of another U.S. drone and caused it to crash into the Black Sea. White House spokesman John Kirby called that incident "unsafe and unprofessional."