European Commission head Jean-Claude Juncker on Monday congratulated Alexis Tsipras on his left-wing party's re-election victory and said Greece has "no time to lose" in implementing the reforms agreed as part of its bailout.
Tsipras secured his second mandate as prime minister this year at a snap general election Sunday that should allow him to drive through unpopular reforms under a third rescue package worth up to 86 billion euros ($97 billion).
"On behalf of the European Commission, I would like to congratulate you on the electoral results of last night," Juncker said in a letter to Tsipras, released to journalists.
"I am confident that this provides the basis for your new government to be formed swiftly and to use the democratic mandate to move forward" on implementing the three-year bailout deal agreed in August.
Juncker warned Tsipras of "the urgent need to operationalise the management of the refugee crisis," in which Greece is on the frontlines, with tens of thousands of migrants flowing inside its borders.
Juncker said that Tsipras could count on the "commission and me personally, to stand by Greece and support the new government in its efforts."
"There is a lot of work ahead and no time to lose," he added.
Earlier a commission spokesman said Greece's creditors -- the EU, the European Central Bank and the International Monetary Fund -- were expected to meet in the next few weeks to conduct a review aimed at releasing new funds under the bailout deal.
With around 90 percent of votes counted, the Syriza party looked set to secure close to an absolute majority in the country's 300-seat parliament, with a smaller nationalist party expected to join forces and push it over the top.
Donald Tusk, the president of the European Council which is hosting the summit, also congratulated Tsipras.
"I hope that the elections will now provide for the political stability necessary to face all the challenges at hand," Tusk wrote in a letter to Tsipras.
"Many of the biggest challenges facing the European Union as a whole are the same as those facing Greece as a country, such as the refugee crisis and the creation of sustainable growth and jobs," he said, adding he expected the new government in Athens "to contribute constructively" to rising to those challenges.