Maia Sandu spoke after the first formal meeting of her coalition Cabinet, which was formed last weekend but had not been able to fully take power because the caretaker government disputed its legitimacy and refused to withdraw.
Sandu's government comprises her pro-European ACUM group and the pro-Russian Socialist Party, which joined forces after months of political deadlock that followed an inconclusive election in February.
But the former ruling Democratic Party — backed by Moldova's Constitutional Court — claimed the government was formed after a postelection deadline and therefore illegal. The crisis had fueled tensions until the Democrats on Friday conceded defeat. The party said Saturday its leader, oligarch Vladimir Plahotniuc, has temporarily left Moldova.
Also on Saturday, the Constitutional Court annulled its rulings that challenged the legitimacy of the new government, formally ending the deadlock. Sandu accused Plahotniuc and his associates of crime and corruption.
"The heads of the mafia group that usurped power and terrorized the citizens of Moldova for years have left the country," she said. "We want to assure you that ... all of those responsible, including Plahotniuc, will be brought back to Moldova and held accountable for all the abuse they participated in."
Although they ceded power, the Democrats still insisted on Friday that the new government is illegal and that a snap election should be held as the way out of the crisis. The U.S. State Department on Friday hailed the party's decision to withdraw, urging restraint during a transition period and promising that Washington "remains committed" to supporting "a more prosperous and democratic future" for Moldova.
One of the poorest countries in Europe, Moldova is plagued by corruption and political turmoil and has been an arena of rivalry between the West and Russia since it won independence after the 1991 collapse of the Soviet Union.
Bringing together a pro-Russian and a pro-EU party, Sandu's government had come as a surprise to many. In a rare show of unity, it has been backed by both Moscow and Western nations. Sandu insisted that improving the EU ties are her government's priority — Moldova's accession bid has stalled over the slow pace of reform — but that Moldova is also open to boosting economic and trade cooperation with Russia.
"The government program states clearly that association with the EU is the basis of our activity," said Sandu, announcing a visit soon by a delegation from Brussels. "You are going to see very soon concrete steps, progress in improving our relations with the EU. "
Vadim Ghirda in Bucharest, Romania, and Jovana Gec in Belgrade, Serbia, contributed to this report.