A Moldovan court has relieved Igor Dodon of his duties as president and appointed former prime minister Pavel Filip as interim president.
Mr Filip immediately dissolved parliament and called snap elections.
Earlier, the court explained its decision to relieve the president by the fact that Mr Dodon had not dissolved parliament as mandated by an earlier Constitutional Court verdict.
Mr Filip's Democratic Party of Moldova had vowed to challenge the legitimacy of a new government formed by the Russian-backed Socialist party and the pro-European Union ACUM bloc.
Mr Dodon is a former chief of the Socialist party and backed the formation of the new government.
ACUM leader Maia Sandu, a former education minister and World Bank adviser, was appointed as the new prime minister, vowing to curb the influence of oligarchs in the east European country.
Her appointment followed months of deadlock after a February election produced a hung parliament.
But the Democrats accused her and the Socialists of usurping power.
They say Mr Dodon had ignored a ruling by the Constitutional Court stipulating that if a government was not formed by 7 June, there would have to be another election.
Moldova has been dogged by political instability and corruption, especially since a scandal known as the "theft of the century" emerged in 2014-2015 in which $1 billion, around an eighth of its economic output, was pilfered from three banks.