Conservative Prime Minister Erna Solberg is in a very close fight with her main rival, the Labour Party's Jonas Gahr Stoere.
Norwegians began voting on Sunday in a parliamentary election whose outcome is too close to call, with opinion polls showing Prime Minister Erna Solberg's centre-right government and the opposition centre-left bloc running neck and neck.
Solberg's Conservatives want to cut taxes if they win a fresh four-year mandate, while the centre-left bloc led by Labour's Jonas Gahr Stoere seeks tax hikes to pay for better public services.
The outcome could also impact Norway's vital oil industry because to form a government either Solberg or Gahr Stoere is likely to depend on one or more parties that seek to impose limits on exploration in Arctic waters off Norway's northern coast.
The 2011 massacre of young Labour members by Anders Breivik continues to cast its shadow and large numbers of newly politicised young voters could hold the balance of power.
TRT World's Simon McGregor-Wood has more on the story.
Latest opinion polls
Polling stretches over two days, from 1100 GMT on Sunday until 1900 GMT on Monday.
For much of the year, Labour and its centre-left allies were ahead in the polls and were favoured to win a comfortable victory, but support for the government has risen as the economy has gradually recovered from a two-year slump.
Opinion polls in September on average have given Solberg's four-party bloc 85 seats in the 169-member parliament, just enough for a majority, while Gahr Stoere and the centre-left are expected to secure 84 seats.
The winner faces tricky post-election negotiations and will have to meet tough demands from small parties to keep their support over the next four years.
The independent Greens want to end all oil exploration, citing concerns over climate change and pollution, while other smaller parties that may be involved in coalition talks also want to limit the award of new exploration acreage in Arctic waters.
The oil and gas industry accounts for almost half of Norway's export revenues.