Exit polls suggest the radical left-wing Syriza party has won the Greece elections by a wide margin.
PM Samarasa said at a news conference: "The Greek people have spoken and I respect their decision. I hand over a country that is part of the EU and the euro.
"For the good of this country, I hope the next government will maintain what has been achieved."
Following the victory, 40-year-old Tsipras said on Sunday (25 January) that Greece is "leaving behind disastrous austerity" and that, "in Greece, democracy will return. The message is that our common future in Europe is not the future of austerity."
Syriza has promised to improve Greece's debt situation by renegotiating with international creditors.
Earlier exit polls revealed that Syriza won between 36-to-38 percentage of total votes with the ruling New Democracy party coming second at 26-to-28 percentage.
Syriza has said the exit polls are "a return of social dignity and social justice."
Far-right Golden Dawn and centrist The River shared the third ranking in exit polls.
Syriza will reportedly secure 150 seats, which is one short of majority.
Syriza spokesman Panos Skourletis told Greek television: "What's clear is we have a historic victory that sends a message that does not only concern the Greek people, but all European peoples."
Meanwhile, UK Prime Minister David Cameron said on Twitter shortly after Syriza's victory: "The Greek election will increase economic uncertainty across Europe. That's why the UK must stick to our plan, delivering security at home."