Warmer weather has caused toxic algae to spread in the Baltic Sea, local media reported on Monday.

Blue-green algae had already covered parts of the Baltic but began to draw closer to Sweden's eastern coast over the weekend as temperatures picked up, daily newspaper Dagens Nyheter reported.

"The algal bloom at sea picked up the pace last week. During the weekend, it seems to have approached land," said Helena Forslund at the monitoring agency Infobaltic.

Sightings of algae -- which can cause diarrhea, vomiting, fever and muscle pain -- have been reported along the southern and central parts of the east coast, with occasional reports further north and on the west coast of the country.

Reports soared during the weekend as the weather turned warmer in much of the country, the newspaper reported.

Authorities regularly advise the public to avoid swimming or being in contact with cloudy water. Children and animals are thought to be especially at risk.