The call came amid growing anxiety among Kiev's Western-backed rulers that Russian President Vladimir Putin - flushed with expansionist fervour - will imminently order an all-out attack on his ex-Soviet neighbour after only being hit by limited EU and US sanctions for taking the Black Sea cape.
"The aim of Putin is not Crimea but all of Ukraine," Ukraine's National Security and Defence Council chief Andriy Parubiy told a mass unity rally in Kiev.
The takeover came as the chill in East-West ties grew stiffer with a charge by Germany -- a nation whose friendship Putin had nurtured -- of a Kremlin attempt to "splinter" Europe along Cold War-era lines.
Europe's most explosive security crisis in decades will now dominate a nuclear security summit opening in the Hague tomorrow that will include what may prove the most difficult meeting to date between US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov.
One of the biggest tests facing the besieged Western-backed leaders in Kiev now comes from restless Russians who have been stirring up violent protests and demanding their own secession referendums in the southeastern swaths of Ukraine.
The region's mistrust of the new team's European values lies from cultural and trade ties with Russia that in many cases are centuries old -- a fact seized upon today by Crimea's self-declared prime minister.