The strike occurred in the Liberec-Vratislavice castle park about 90 kilometres (55 miles) northeast of the capital Prague on Sunday afternoon.

"There were 18 injured people on the site, including seven serious injuries," local emergency spokesman Michal Georgiev told AFP, adding that the injured had been taken to hospitals.

Liberec regional hospital spokesman Vaclav Ricar told AFP that five adult patients had to undergo resuscitation and that one child was transported to a Prague hospital by helicopter.

"They were all conscious and their condition was stable," he said, adding the patients did not suffer any burns.

Local firefighters said on X that the lightning "struck a tree under which there were people".

Media reports said the castle park was holding an event to mark Saturday's International Children's Day.

The Czech Republic was hit by heavy rain on Saturday and storms on Sunday.

Heavy rain also caused floods in neighbouring Germany over the weekend, with one volunteer firefighter reported dead and another missing on Sunday.