More than 20 people are feared dead in the worst flooding to hit the Balkans in a century.
The floodwaters caused by days of record rainfall has forced tens of thousands of people to flee their homes.
The worst hit are Bosnia-Herzegovina, where at least 16 people died, and Serbia.
A spokesman for Bosnia's Security Ministry said about 1 million people, or over a quarter of the country's population, live in the affected area.
Authorities warned that mines laid during Bosnia's 1992-95 war could be moved by floods and landslides increasing the risk of deadly incidents.
In Serbia, meteorologists have warned that the flooding on the Danube and Sava rivers was expected to peak on May 18.
Poland, Slovakia, and Austria also saw less severe flooding after torrential rains across eastern Europe.
Based on reporting by Reuters, AP, dpa