Emden, Germany - Some 23 people were injured when a catamaran ran into heavy seas off the north German coast, police said Tuesday.

The vessel was on its way from the North Sea island of Heligoland to the port of Borkum on Monday evening when metre-high waves tore off a guard rail and sent it smashing through a panorama window.

Flying glass injured 23 of the passengers, including three who were so badly hurt that they had to be transported by helicopter to a hospital on the mainland.

Heligoland attracts thousands of day-trippers during the summer months, most of whom make the trip by sea. (dpa)