Three people were taken to hospital after a train derailed in eastern Sweden when a railway embankment collapsed following heavy rains, police said, as weather agencies warned of more flooding.

The passenger train, which was carrying some 120 people, was headed to the city of Sundsvall when two of its four cars derailed near the city of Hudiksvall shortly after 12:30 pm (1030 GMT).

After police and rescue services arrived at the scene it was "determined that the railway embankment had been undermined by the heavy rain and collapsed."

"Currently, three people have been taken to hospital, the extent of their injuries is unclear," police said in a statement.

Sweden's national weather agency SMHI had issued several "yellow alerts" for Monday, warning of strong winds, floods and heavy rains in multiple parts of the country as extreme weather "Hans" moved in across the country over the weekend.

The agency's alerts go from "yellow" through "orange" to "red," and SMHI had also issued red alerts -- signalling "very serious consequences for society" -- for flooding on Tuesday and Wednesday.

A similar warning was issued by the Norwegian Meteorological Institute on Monday, which especially warned of "extremely heavy rainfall" in the country's southern parts.

"In many places, the event will be among the strongest in the last 25 years," the weather agency said.