The incident took place in Skänninge, a town of around 3000 residents, near Mjölby in Östergötland county around 200 kilometres south-west of Stockholm, reports regional newspaper Corren.
A woman called the police at 1am to report that she had been harassed by two people dressed up as clowns and brandishing what police described as a large knife.
“They also shouted death threats at the woman,” police control room officer Torbjörn Lindqvist told the newspaper.
With clown sightings multiplying this month in the UK, British police this week asked people not to go outside dressed as clowns. And Swedish police warned people not to participate in the trend.
“What is meant as a joke could end up with you sitting in a police cell suspected of aggravated threat – then the joke might not be as funny any more,” said Lindqvist.