A tornado left 43 people injured as it "cut a path of destruction" through several towns in western Germany, police said.
Officers in the city of Paderborn said the tornado ripped off roofs and debris was strewn around for kilometres.
Ten people have serious injuries and one woman's life is in danger, they said.
A 38-year-old man also died in severe storms which lashed the region on Friday.
Police posted images showing trees felled or split in half and roofs stripped of tiles, while images on social media appeared to show a tornado's spinning column of air flinging debris.
"Sheet metal, insulation and other materials were blown kilometres away. Countless roofs are covered or badly damaged. Many trees still lie on destroyed cars," said police in Paderborn, which has a population of about 150,000.
Local media quoted police as saying the 38-year-old man died in the town of Wittgert, about 180km (111 miles) south-west of Paderborn.
He suffered an electric shock in a flooded cellar, police said.
A fire department spokesperson told the AFP news agency that the town of Lippstadt, about 30km (18 miles) from Paderborn, was also probably hit by a tornado - although no injuries were reported.
Images on social media showed that in nearby Hellinghausen, a steeple had been ripped off the roof of a church tower, with the rubble scattered in the churchyard.
BBC Weather presenter Chris Fawkes said that Germany usually experiences several tornadoes a year, but most are short-lived and do not cause significant damage.
He said the number of tornadoes reported in Europe has been increasing in recent years, but this is largely thought to be a result of better forecasting and more awareness - and includes the advent of social media reports.
"As to whether climate change is also playing a role too, that's still a subject of debate," he said.