'Destructive force'

Across Poland dozens of roofs were ripped off houses, basements and roads were flooded and numerous cars were damaged.

Those killed included a 24-year-old pregnant woman in Chojne, near Sieradz, in central Poland, who died when a tree branch crashed onto her car.

The body of a 67-year-old man was found crushed beneath a tree in a park in Legnica, in the southwest of the country.

In Krotoszyn, in western Poland, seventeen people were injured when a broken high voltage power line fell on them, Fratczak said. Six suffered serious burns.

IMiGW, Poland's state weather service, said the unusually violent storms were caused when hot air masses from north Africa  clashed with cooler air systems moving in from Western Europe.

Maria Waliniowska, an IMiGW press officer, said: "That's what unleashed this enormous destructive force."

More than 12,000 Polish firefighters were said to tackling the aftermath of the storms.

Capsized boat

High winds also claimed two lives and injured dozens in the neighbouring Czech Republic.

A 75-year-old woman was killed in the northern town of Hradek nad Nisou by falling tree branches, while the body of a man presumed drowned was found after a boat capsized on a river south of the Czech capital Prague.

In Germany, a driver was killed Thursday night when he lost control of his car during heavy rains and hit a highway guard rail.

In Austria, hail pounded 60,000 hectares (148,000 acres) of crops, causing estimated damage of $28.4m, the Osterreichische Hagelversicherung insurance company said.

High voltage power lines were downed and rail traffic was disrupted in Slovakia. 

Storms were still battering parts of Poland on Friday, but forecasts suggested they would not be as violent as those of the previous night.