Raging waters from three rivers have poured into the old town of Passau in south east Germany, one of the cities worst hit by the flooding that has spread across a large area of central Europe.
Rescuers used boats to transport residents from flooded parts of the city to dry land as officials warned that water levels - already the highest in 70 years - could rise further.
A spokesman for the city's crisis centre said much of Passau was inaccessible on foot and the electricity supply had been shut down as a precaution.
"The situation is extremely dramatic," spokesman Herbert Zillinger said.
Water from the Danube, Inn and Ilz rivers rose above markers set in 1954, when the city suffered its worst flooding in living memory. Mr Zillinger said levels would continue to rise throughout the day.
At least six people are reported to have died and seven are missing due to floods in Germany, Austria, Switzerland and the Czech Republic following days of heavy rainfall.
Czech authorities were working to erect further protective metal barriers along the Vltava river, which also flows through the capital Prague.
Interim mayor Tomas Hudecek said no major evacuations were planned, but animals from a zoo located by the river have been taken to safety. Parts of the city's subway network have also been shut down because of flooding.
The German army has deployed hundreds of soldiers to help local authorities and volunteers reinforce flood defences, particularly in the south and east of the country.
Chancellor Angela Merkel plans to visit flood-hit areas tomorrow, her spokesman said.
In the Czech Republic, the Charles Bridge - normally packed with tourists at this time of year - has been closed to the public as have some other popular spots near the river at the foot of Prague Castle.
Rescuers have evacuated some 2,700 people across the western half of the country where the government declared a state of emergency in most regions.
Some people had to leave their homes in the southern neighbourhoods of Prague while further evacuations have been under way in the north, awaiting a flood wave expected later today.