Three days of heavy rain have caused landslides and floods in central Switzerland, cutting off villages and killing at least two people.
The bad weather seriously disrupted the traffic network and forced the authorities to close the main north-south rail links.
President Samuel Schmid, who is also defence minister, visited the disaster region around Lake Lucerne on Monday. He pledged government aid for the worst affected areas.
Several hundred soldiers have already been deployed to support the civilian authorities, according to army officials.
Flooding stretched from western Switzerland to the northeastern city of St Gallen as rivers and lakes burst their banks.
The damage caused by the bad weather is estimated at SFr100 million ($79 million). It is the worst flooding in Switzerland for several years.
Thousands of people had to be evacuated from homes in towns and villages, notably in central Switzerland as well as in and around the capital, Bern.
The authorities said two firefighters were killed by a mudslide on Sunday night in the Entlebuch region near Lucerne when they tried to help evacuate a farm.
Flooding in suburbs of Lucerne led to power cuts. Schools remained closed in many towns and supplies of drinking water were polluted.
The authorities said transalpine train services were suspended because of the bad weather and the risk of landslides. The Lötschberg line in western Switzerland is due to re-open on Tuesday morning, according to railway officials.
Dozens of roads, including the main motorway to the Gotthard road tunnel, were closed, police said.
Navigation along the River Rhine near Basel was brought to a standstill.
Experts said water levels of many rivers and lakes were likely to rise in the next few hours.
Up to 110mm of rain had fallen in parts of central and western Switzerland by Sunday.
The downpour continued on Monday as bulldozers cleared mud from the streets and firefighters pumped water from flooded basements in towns across the country.
Swiss Solidarity, the fundraising arm of the Swiss Broadcasting Corporation, swissinfo's parent company, has launched an appeal for the victims of the disaster.
swissinfo with agencies
At least two firefighters were killed and thousands of people were evacuated because of torrential rains over the weekend.
The flooding and mudslides are estimated to have caused damage of up to SFr100 million ($79 million).
Since the 1970s, natural catastrophes have claimed the lives of nearly 100 people in Switzerland.
The damage caused by avalanches, flooding and landslides is estimated to have cost more than SFr9 billion over the past three decades.