The former foreign minister of the Czech Republic, Karel Schwarzenberg, has accused Vladimir Putin of acting like Hitler in 1930s Europe after moving Russian troops into Ukraine's Crimean pensinula.
"What's happening in Ukraine is history repeating itself," Schwarzenberg told Austrian publication Osterreich.
He said Putin was "acting on the same principles as Adolf Hitler" when he sent Nazi troops into Austria, Czechoslovakia and Poland in the late 1930s, sparking World War II.
Putin ordered troops in on the grounds of protecting Russian interests, including the massive Black Sea Fleet and the majority ethnic Russian population, after Ukraine's president Viktor Yanukovich was toppled in a popular uprising.
"Since he wanted to invade Crimea, he needed a pretext and said that his compatriots were oppressed," said Schwarzenberg.
"When Hitler wanted to annex Austria, he said that Germans there were oppressed," he continued.
"Europe should clearly tell him that this is a violation of law that will not pass."
Another prominent Eastern European figure slammed Russia's invasion of Ukraine. Ukraine's first president, Leonid Kravchuk, said he would take up arms to defend his homeland if Moscow does not retreat from the Crimea region.
The region lies in the southern part of Ukraine on the Black Sea. The Black Sea Fleet is stationed at Sevastopol and 60% of the region's population are ethnic Russians.
The Russian elite views Ukraine as part of the Soviet sphere of influence and sees the country as a potential bulwark against the growth of EU liberalisation.