BERLIN (AP) — A tornado in the German port city of Kiel has injured several people, four of them seriously, authorities said.

The city's fire service said dozens of first responders were involved in an operation to rescue a group of rowers who were surprised by the twister Wednesday as it swept along the Baltic Sea front.

Videos posted on social media showed a tree being uprooted and chairs and other objects being sucked into the air by the waterspout that formed at about 6 p.m. (1600 GMT; 12 p.m. EDT).

German news agency dpa on Thursday quoted an official at the country's national weather agency DWD saying the tornado was likely not very strong, but could have caused significantly more damage if it had hit the city center rather than a largely unpopulated area.

There are about 20 to 60 tornadoes each year in Germany, according to the European Severe Weather Database.