Sweden's election was too close to call after more than 86% of ballots had been counted on Sunday night.
Former Prime Minister Magdalena Andersson, whose Social Democrats lead a left-wing opposition coalition and is hoping to return to power after four years, said early on Monday morning that "it looks like it will be very close."
"We Social Democrats will always be ready to assume responsibility for the result... For now, we are in the lead. And if that is confirmed, Sweden will have a new government," she told supporters.
The center-left party was on course to win 28% of the vote, which would be its worst result in over a century.
Incumbent Ulf Kristersson, who leads a right-wing alliance that includes the far-right Sweden Democrats, said he would reach out to other party leaders for discussions, and that it was unclear who would be governing the country in the coming years.
