Lithuania has marked the 25th anniversary of its declaration of independence from the Soviet Union amid warnings that its freedom could once again come under threat.

In celebrations overshadowed by Moscow's intervention in Ukraine — another former Soviet republic — Lithuania's first post-independence president Vytautas Landsbergis told lawmakers Wednesday not to take freedom for granted or "our success story may soon become a temporary success story."

Current President Dalia Grybauskaite urged Lithuanians to show strength and courage as "the rattle of the guns is heard" from the east.

Lithuania, now a member of NATO and the European Union, became the first Soviet republic to declare independence on March 11, 1990. But it only achieved its freedom over a year later after a failed communist coup in Moscow.