At least 20,000 people gathered in the capital of Moldova on Sunday, calling for the resignation of the government and the dissolution of parliament.
The protesters were responding to a demand from the newly elected pro-European president Maia Sandu, who is due to take office at the end of the year.
The demonstrators, whose estimated numbers were confirmed by AFP journalists on the ground, shouted "resign!", "early elections!" or "down with thieves, down with corruption!" while wearing masks to protect against spreading coronavirus.
Sandu was the surprise winner of the presidential election in the small ex-Soviet republic between Ukraine and Romania, beating pro-Russian Igor Dodon in November.
The opposition has already demonstrated this week against new laws reducing presidential powers brought in by the government.
One of these laws transfers control of the security services (SIS) to deputies, which Sandu and her supporters believe is a way to reduce the role of the presidency at the expense of parliament, controlled by Dodon.
Speaking at the rally on Sunday, the president-elect said "Igor Dodon does not want to admit defeat. He wants to set fire to the country, cause chaos, isolate Moldova internationally. To do this, he uses thieves and corrupt officials in parliament.”
"We want Moldova to develop, so that all the thieves go to prison and the citizens of the country can live in peace and harmony," she said.
Moldova is divided between supporters of a rapprochement with Moscow and those who support European integration, particularly through the country's links with neighbouring Romania.
Sandu’s victory marked a setback for Russia, which is anxious to preserve its influence over the country and whose army is deployed in Transnistria, a pro-Russian territory that has seceded from Moldova.
Moscow openly supported outgoing President Igor Dodon.