Swedish Prime Minister Stefan Lofven went into self-isolation on Thursday after someone close to him got into contact with someone who tested positive for COVID-19.

The 63-year-old announced in a Facebook post that he had tested negative but would still self-isolate with his wife on the advice of his doctor.

The Prime Minister warned that Sweden's COVID-19 situation was getting worse as the death toll surpassed the 6,000 mark.

"More people are infected. More people are dying. It is a serious situation," he said.

By Thursday afternoon, the country had reported 141,764 confirmed COVID-19 infections, according to the Johns Hopkins University.

In the last 24 hours, 4,034 new cases were reported, with five new fatalities that took the country's total death toll to 6,002.

In response to the surging figures, the Swedish government has imposed stricter measures for the heavily hit areas.