Eight people died and thousands were forced from their homes after heavy rain fell across northern Italy, officials said on Wednesday.
It is the second time in two weeks that Emilia Romagna, which is one of Italy's richest regions, has been deluged with rain.
Torrential rain and landslides were reported in Croatia, Bosnia and Slovenia, but Italy has suffered the worst of the weather.
This weekend's Italian Formula One race in Imola, which is close to many of the worst-hit areas, was called off as emergency services concentrate on the rescue operation.
Two bodies were recovered by divers working in the city of Forli on Wednesday morning as part of a rescue effort that included the armed forces.
“The city is on its knees, devastated and in pain,” said Forli mayor Gian Luca Zattini. “It's the end of the world.”
About 50cm of rain fell within 36 hours in Forli, Cesena and Ravenna – or about half the normal annual rainfall, Civil Protection Minister Nello Musumeci said.
“It is still a very critical situation,” he said.
Rivers burst their banks, inundating towns and submerging thousands of acres of farmland.
Rescue teams worked through the night to save children, the elderly and the disabled from the rising waters.
“We're scared - this time we're scared,” said Simona Matassoni, owner of the Hotel Savio in Cesena, which had escaped the flooding.
“I've seen lots of full rivers, but never anything like this. At the moment we're crossing our fingers … but another flood is expected, so who knows (what will happen),” she said.
Mr Musumeci said about 4,000 people had left their homes and 50,000 people were without electricity.
All the rivers in the region had broken their banks on Tuesday and Wednesday, and 24 local authorities reported flooding.
The civil protection agency urged “maximum caution” and mayors advised people to stay on high ground.
In Forli, streets became rivers and firemen took residents to safety in rubber dinghies.
Elsewhere, muddy water rushed under the arches of walkways in Bologna, while residents in Cesena swam down a road to rescue a three-year-old child.
In the Balkans, the swollen Una river flooded parts of northern Croatia and northwestern Bosnia, where authorities announced a state of emergency.
The mayor of Bosanska Krupa in Bosnia said hundreds of homes had been flooded.
“We have an apocalypse,” Amin Halitovic said. “We can no longer count the flooded buildings. It’s never been like this.”
Dozens of landslides were reported in eastern Slovenia, many of which endangered homes and infrastructure.
In Croatia, hundreds of soldiers and rescue teams to take food and other necessities to people in flood-hit areas who have been isolated in their homes. No casualties have been reported.
At least eight killed after flooding in northern Italy
