Lake Thun, 25 kilometres (15 miles) south of the Swiss capital Bern and on the edge of the Alps, reached the high water level of 558.3 metres above sea-level early on Thursday and was expected to overflow later in the day, town authorities said in a statement.

Fire services and civil protection units worked overnight to help people seal their ground floor entrances and cellars, and the 41,700 inhabitants were advised to listen to the radio.

"If the level carries on rising, we will ask for help from neighbouring towns," Thun official Hans Ueli Gerber told the Swiss news agency ATS.

The river Aar, which flows through Bern, has also risen in recent days because of heavy rain in the Swiss Alps.

TERRA.WIRE