Standing in the shadow of a massive, grey former KGB building in a busy Vilnius street, Lithuanian pensioner Rimantas Gucas worries history could repeat itself if the West fails to stop Russia from absorbing Ukraine's Crimean peninsula. As Lithuania marks 24 years since it broke free from the crumbling Soviet Union and a decade since it joined NATO, people here and in fellow Baltic states Estonia and Latvia are jittery over Russian moves in Crimea. Russian President Vladimir Putin is a "madman" who "won't stop until he's stopped by force," Gucas, 72, who grew up under Soviet occupation, told AFP. "Should we in the Baltic states be worried too? Ukraine reminds us of the takeover of Czechoslovakia in 1938. Should we now wait for a repeat of the 1939 attack on Poland?" he said, recalling the moves by Nazi German dictator Adolf Hitler that sparked World War II. The former KGB Soviet secret-service building in Vilnius is now a court and museum with the names of partisans who fought Soviet occupation from 1944-1953 carved on its stony wall. Soviet troops also killed 14 civilians when they stormed a Vilnius television tower in January 1991 in a failed bid to crush independence. "I think Putin should be called 'Putler' or 'Stalin II'," said Vilnius pensioner Birute Jurksiene, comparing the Russian president to Hitler and Soviet dictator Joseph Stalin. "The West didn't suffer like we did, so they just can't understand." The USSR occupied and then annexed Estonia, Latvia and Lithuania during World War II. Mass deportations to Siberia and Central Asia followed. The trio remained firmly under Moscow's thumb until Kremlin leader Mikhail Gorbachev came to power and began the Perestroika and Glasnost political and economic reforms, which triggered the USSR's collapse in 1991. Lithuania, where about six percent of the population are Russian, was the first Soviet republic to declare independence on March 11, 1990. Estonia and Latvia were quick to follow. All three joined the EU and NATO in 2004 in a bid to seal their independence from Moscow. - NATO shield - But an invitation to independence festivities in Vilnius on Tuesday posted by organisers on Facebook warned that events in Ukraine prove that "independence and freedom can be very fragile, even today". Also comparing Putin to Stalin, Lithuanian President Dalia Grybauskaite starkly warned that Russia is "dangerous" and "unpredictable" during a recent emergency EU summit in Brussels focused on Ukraine. "This is about rewriting borders," the tough-talking former EU budget chief said, pointing to Crimea. The EU is mulling economic sanctions against Moscow over its actions there, with hawkish Eastern European members pushing the hardest. Vilnius University analyst Kestutis Girnius is, however, more circumspect about the threat posed by Moscow. He said EU and NATO membership make the Crimea scenario highly improbable in the Baltic states. "Since NATO would lose all credibility if it failed to defend them, it has an overriding motive to come to their defence. Russia knows this, and thus will avoid tempting fate," he told AFP. Moscow has special links to Crimea, which was transferred from Russia to Ukraine in 1954 when they were both part of the USSR. That is not the case for the Baltics, he added. "The Soviet occupation of the Baltic states was never recognised by the West and Moscow grudgingly accepted 'Baltic exceptionalism'. Russia made clear its opposition to Baltic entry into NATO, but made no serious efforts to halt the process," Girnius explained. But Moscow's brief 2008 war with ex-Soviet Georgia and Russian military exercises focused on cutting off the Baltic states from the rest of NATO sparked concern. As the Crimea crisis escalated, Washington sent six additional F-15 fighter jets Thursday to step up NATO's Baltic air policing mission from a base in Lithuania, expanding the squadron to 10. - Promises - Lithuanian Defence minister Juozas Olekas called the deployment a response to "Russian aggression in Ukraine and additional military activity in the Kaliningrad region," Russia's exclave bordering Lithuania and fellow ex-communist NATO member Poland. Moscow slapped trade restrictions on Lithuania last year -- a move Vilnius dubbed retaliation for its key role in efforts to seal an EU association pact with Ukraine. Ousted president Viktor Yanukovych rejected the agreement in favour of an aid deal with Russia, sparking the protests that ultimately led to his ouster last month. Moscow's promises to "defend" ethnic Russians in Crimea have set off alarm bells in Latvia and Estonia, where Russian-speakers make up around a quarter of population. Latvia’s Foreign Minister Edgaras Rinkevics recently tweeted that the "Crimea scenario resembles occupation of the Baltic states by the USSR in 1940". Leonid, one of Latvia's 300,000 Russian-speakers, insists Moscow has no business in Ukraine. "Military force just isn't right," the 60-year-old told AFP in the capital Riga. "It's a tragedy that Russians and Ukrainians are against each other when we're brothers," he added. But the largest party in Latvia's parliament has refused to condemn Russia outright. Supported mainly by ethnic Russians and with ties to Vladimir Putin's United Russia party, the Harmony Centre said that both Moscow and Kiev were to blame for tensions. Enn Tart, a Soviet-era dissident in Estonia, warned Russia "will always make demands on its neighbours, as it has done for centuries". "But I hope the EU and US will finally understand that Putin should be stopped," he said.