Magdalena Andersson is seeking to return as prime minister - a job she held from 2021 to 2022
Sweden's general election remains too close to call, early results suggest.
With 50% of the votes counted, the two main blocs were separated by only 20,000 votes, Sweden public broadvasteer SVT said.
Exit polls had given the left-wing political bloc led by Social Democrats leader Magdalena Andersson a small lead over the rival four-party coalition put together by current conservative Prime Minister Ulf Kristersson.
Kristersson has been supported in government by the hard-right Sweden Democrats (SD), which have neo-Nazi roots. He has promised cabinet jobs for the SD if he stays in charge, but partial results suggest the party was losing support for the first time since 2010 when it entered parliament.
Close race in Sweden as hard right eyes role in government
Sweden has two major political blocs featuring four parties on the right and four on the left - meaning coalition and minority governments are relatively common.
Andersson's party, the Social Democrats, have been a major force in Swedish politics since the end of World War Two.
But SD - founded by Nazi sympathisers in the 1980s - had been shunned for years until 2022 when it became the country's second largest party after campaigning on violent crime and immigration.
After casting her vote on Sunday, Andersson laid out the choice facing the Swedish public: "Should we have a government entirely dominated by the Sweden Democrats, something that has never happened in Sweden before? Or should we have a government led by me, which will steer Sweden in a new spirit of co-operation?"
Kristersson, for his part, said it was important he and his alliance were able to continue their work.
"I think there is a genuine enthusiasm for us being able to continue our important work," he said after casting his ballot in his home municipality of Strangnas.
National security, gang crime and welfare spending dominated the election campaign.