With 95.1 per cent of votes counted on Tuesday morning, the Conservatives, along with their coalition partner the Progress Party (FRP) and two other centre-right allies, were projected to win 89 seats in the 169-seat parliament, according to a forecast by Norway’s Election Directorate.
Mrs Solberg’s re-election marks the first time in more than 30 years a Conservative prime minister has won a second straight term.
She told a rally of supporters in Oslo: “We have to be a little cautious, but it looks as though we will have a non-socialist majority.”
The opposition, led by Labour leader Jonas Gahr Støre, has so far taken 80 seats.
Mr Støre, who has previously served as the country’s foreign minister, conceded defeat and wished his rival well.
He told supporters: “This is a big disappointment for Labour.
“Our goal was to give Norway a new government. We knew it was going to be close, and it was close.
“But as it looks now it wasn’t enough to replace a Conservative-Progress Party government with a Labour government.”
The Labour Party received 27.3 per cent of the votes and 52 mandates, a sharp decline from the previous elections when the party won 30.8 per cent and 55 mandates.
Both the Green Party (MDG) and the Red Party (Rødt) landed less than the four per cent threshold needed for gaining extra representatives in parliament.
The Liberal Party (Venstre) and the Christian Democrats (KrF) cleared the threshold.
The Centre Party (SP) is the election’s biggest success story after it gained 10.5 per cent of the votes – almost five percentage points up from the election four years ago.
Mrs Solberg thanked coalition party leaders Siv Jensen (Progress Party), Trine Skei Grande (Liberal Party) and Knut Arild Hareide (Christian Democrats) in her speech and said she has invited the three to a conversation about future collaboration.
Mrs Solberg added: “I’m sure we will find good solutions for the four parties during the next four years.”
Mrs Jensen, moved to tears by the election result, said: “Think back four years ago. Think of all the predictions then of people who rubbed their hands and looked forward to bullying Progress in government. Absolutely all those predictions are put to shame.”
The centre-right government will be dependent on the support of all centre-right allies in Parliament.
The Conservatives and Labour agree on issues such as continued oil activities in the Arctic, a restricted immigration policy and close ties with the European Union.
But Labour has criticised Mrs Solberg for her difficulties in taming her on occasions provocative partner the Progress Party.