In Paris, lightning struck a group of children and adults in Parc Monceau, a few blocks north of the Champs-Élysées. Four people -- three of them children -- suffered life-threatening injuries. Two others were in critical condition and five in serious condition, authorities there said.
The group had gathered for a birthday party when a storm broke out, CNN affiliate BFMTV reported. They sought shelter under a tree.
A total of eight children and three adults were injured, an official with the Paris Police Prefecture told CNN.
Off-duty firefighter Pascal Gremillet was walking near the park when he heard the lightning strike the tree, he told CNN affiliate BFMTV.
"I saw immediately that one of the children was in cardiac arrest, so I provided them with first aid," he said on another network.
Parc Monceau is a popular spot in the French capital's 8th arrondissement, with trees, statues, playgrounds and a pond attracting visitors and tourists alike.
In Germany, three adults were severely injured and 29 children were sent to hospitals as a precaution when lightning struck during a local soccer match in western Germany, police told CNN.
The umpire for the match, a 45-year-old man, was struck by lightning as he blew the whistle to end the game in the town of Hoppstaedten, according to Lauterecken Police Chief Sabine Beck.
The man's heart stopped but he was revived by spectators and first responders at the scene, Beck said. He was later transported by helicopter to a hospital.
Two other adults sustained severe injuries in the the lightning strike and were also transported to hospitals, officials said.
A total of 29 children ages 9 to 11 years old were playing on the field when the lightning struck and were sent to nearby hospitals as a precautionary measure, the police official said. No children were hurt, she added.
When the lightning struck there were severe weather warnings in the area but the sky above the soccer field was clear, Beck said. She called the incident "unpredictable."