French President Francois Hollande on Wednesday said Russian move to annex Crimea was "unacceptable," urging Moscow to withdraw its troops to pave the way for a democratic transition in Kiev.

During a phone conversation with his Russian counterpart Vladimir Putin, Hollande pointed to "the specific gravity of the current situation in Ukraine," adding that the Crimea referendum on whether to join Russia "has no legal basis" and would be "unacceptable by the international community."

In a communique released by the presidential office, Hollande asked Moscow to do everything to prevent the annexation of Crimea.

Crimea, a Russia-leaning autonomous republic of Ukraine, was set to hold a referendum on Sunday over its future status.

The French president stressed to "avoid unnecessary and dangerous escalation" via a crisis exit plan, urging respect of Ukraine sovereignty and territorial integrity, pullout of Russian troops from the Black Sea Peninsula and a transparent presidential elections in the crisis-hit country.

The Ukraine crisis, which originated from protests against former President Viktor Yanukovych's decision last November to abandon an association agreement with the European Union for Russian aid, took an abrupt turn in the past two weeks following bloody clashes between protesters and police. Yanukovych was ousted and then forced to flee Kiev.

Since the outbreak of the political turmoil, Kiev has been accusing Moscow of inciting separatist sentiments and deteriorating the situation in Crimea by increasing military troops in the peninsula, an accusation denied by Moscow.

Crimea, host to Russia's Black Sea Fleet, has remained the epicenter of the ongoing crisis.