"We, the foreign ministers of Estonia, Latvia and Lithuania condemn in the strongest possible way the open large-scale Russian aggression against the independent, peaceful and democratic Ukraine," they said in a statement that was posted by the Lithuanian Foreign Minister Gabrielius Landsbergis on Facebook.
Russia's actions are unacceptable and are a flagrant violation of international law and norms, and a crime against the Ukrainian people, according to the ministers.
"All of us in the whole international community needs to condemn it in a strongest possible way, to impose strongest possible sanctions on Russia, including disengaging Russia from SWIFT, isolating it politically," they said.
There is an urgent need to provide Ukraine with weapons and ammunition and other military assistance, as well as economic and humanitarian aid, according to the statement.
Cutting Russia off from the SWIFT international interbank settlement system would make most financial transactions with the country impossible.
In the early hours of Thursday, Russian President Vladimir Putin announced a "special military operation" in Ukraine to defend pro-Kremlin separatists and "demilitarize and denazify" its western neighbor.
Shortly after he spoke, explosions were heard in Kyiv and several other cities.
Earlier this week, Western countries announced their first package of sanctions against Russia.