There are eight parties running to win seats in the 349-seat parliament, or Riksdag. They belong to one of two major blocs, one with four left-wing parties and another with four conservative parties.
Two exit polls have given Sweden's left-wing bloc led by Social Democratic Prime Minister Magdalena Andersson a slim lead in the country's general election, while also indicating a far-right surge.
The four left-wing parties were credited with 50.6 percent of voter support in an exit poll published on TV4 on Sunday, compared to 48 percent for the four parties on the right.
A second exit poll on public broadcaster SVT gave the left 49.8 percent and the right 49.2 percent.
Both polls, published after voting closed on Sunday, also suggested that the anti-immigration and nationalist Sweden Democrats could for the first time become the country's second-biggest party.
They credited the party with 21.3 and 20.5 percent of votes respectively.
If the exit polls are confirmed, the far-right surge would mean they overtook the traditional leaders of the right-wing bloc, the conservative Moderates, whose party leader Ulf Kristersson is challenging Andersson for the post of prime minister.
That would be a heavy blow to Kristersson, who orchestrated a major shift in Swedish politics by initiating exploratory talks in 2019 with the Sweden Democrats, long treated as "pariahs" by other political parties.
The two other small right-wing parties, the Christian Democrats and to a lesser extent the Liberals, later followed suit.
Sweden's local, parliamentary, and regional elections occur every four years on the second Sunday in September. Up to 7.5 million Swedes are expected at the polling booths on the 11th of Sept. Here is our film on the subject! pic.twitter.com/ndUXo14l3c— Sweden (@Sweden) September 6, 2022
If the final results were to confirm the left bloc's lead, Prime Minister Andersson, a 55-year-old former finance minister, would try to build a government with the support of the small Left, Centre and Green parties.
For a number of reasons there is "pressure to have a united and effective government" in place quickly, said political scientist Katarina Barrling.
The Social Democrats have governed Sweden since 2014.
Voter turnout was expected to be high, with more than 80 percent of the country's 7.8 million eligible voters expected to cast ballots.
Andersson, whose party has dominated Swedish politics since the 1930s, enjoys broad support among Swedes.
She consistently led Moderates leader Kristersson by a wide margin in opinion polls.
The election campaign has been dominated by rising gang shootings, immigration and integration issues, and soaring electricity prices.