Ukrainian missiles appear to have hit a Russian military base in Millerovo, a Russian town 16 kilometers from the border of the two countries, according to unconfirmed social media posts.
Russian President Vladimir Putin on Thursday declared war on Ukraine, a move that has drawn scathing criticism from most military powers except for China.
At least 137 Ukrainians have died and hundreds more have been injured as Russia continues its invasion.
At least 800 Russian soldiers have also reportedly lost their lives.