Alexis Tsipras

The EU is expected to renew sanctions in a matter of weeks.

Alexis Tsipras was speaking at a joint news conference in Athens with the Russian President Vladimir Putin.

Mr Putin said there would be "no discussions" about Crimea, the Ukrainian peninsula that was seized by Kremlin-backed forces in 2014, leading to sanctions from the EU and US.

The territory, which has an ethnic Russian majority, later voted to join Russia in a referendum that Ukraine and Western countries deem illegal.

Labor Minister George Katrougalos said the new administration elected Sunday has to focus on the reforms that were a key condition for the latest in a series of international bailouts keeping the country afloat.

"Until now the people knew us and backed us as a force of resistance to neoliberalism, establishment politics and corruption," he said at a swearing-in ceremony for Prime Minister Alexis Tsipras' new government. "Now we must prove that we are also a force for reform."

Syriza's victory in Sunday's election marks a personal triumph for Tsipras, who served as prime minister between January and August — a tumultuous period that saw Greece's future in the 19-country eurozone come under real threat and strict banking controls imposed.

At 41, Tsipras dominates Greek politics despite a major policy U-turn that saw him go against the anti-austerity platform that swept him to power in elections in January in return for a multibillion bailout that keeps Greece in the eurozone.

The result was a resounding success for Tsipras' high-risk gamble when he resigned as prime minister last month and triggered an early election, barely seven months into his four-year term, in order to face down an internal Syriza rebellion over his policy U-turn to accept painful austerity measures in return for Greece's third international bailout.

Three surveys published Friday show the two parties roughly level within the margin of error, with the winner likely to require the support of two smaller parties to form a coalition government.

Syriza leader Alexis Tsipras resigned as prime minister and called the snap election last month after reaching an agreement with eurozone creditors for a third bailout that triggered a split within his party.

Greeks go to the polls on Sept. 20 with former prime minister Alexis Tsipras seeking a stronger mandate to implement unpopular reforms needed to secure the 86 billion euros ($97 billion) rescue program.

Eurogroup chief Jeroen Dijsselbloem said Saturday that renegotiation is "not possible" regardless of who wins "so work must continue" on reforms required to secure the loans.

Speaking after chairing a meeting of the 19-nation currency bloc, he said that finance ministers had not discussed any debt relief for Greece.

Alexis Tsipras resigned last month, triggering Sept. 20 elections, barely eight months into his four-year term following a rebellion by Syriza hardliners objecting to his agreement to creditor-demanded tax hikes and spending cuts in return for a third bailout.

Recent opinion polls show Syriza in a dead heat with opposition New Democracy, but with neither winning enough seats to form a government.

Prime Minister Vassiliki Thanou, a top judge, and her cabinet will lead the country to elections expected to be on Sept. 20, following outgoing prime minister Alexis Tsipras' resignation last week.

He stepped down following a rebellion by members of his radical-left Syriza party who objected to his agreement with the conditions of Greece's third international bailout.

Supreme Court head Vassiliki Thanou, 65, was appointed after radical left Prime Minister Alexis Tsipras resigned, seeking a stronger mandate to implement tough austerity measures demanded by Greece's creditors in return for a third bailout worth 86 billion euro ($97 billion).

Her main task will be to hold the reins until a new government emerges from the vote expected on Sept. 20.

They are trying to prevent Greece from holding its third national vote this year, although chances of averting the election are virtually nil.

Former Energy Minister Panagiotis Lafazanis, who heads the newly formed Popular Unity, received the maximum three-day mandate from the country's president after the head of the main opposition conservative New Democracy failed to form a government.