Police say three German tourists have died after a ship's mast broke and fell on them in a northern Dutch port.

Friesland provincial police say in a tweet that investigations are underway to establish exactly how the mast broke on Sunday when the ship was near the port town of Harlingen, some 110 kilometers (68 miles) north of Amsterdam.

Police say the victims, whose identities were not immediately released, were part of a family group of 12 Germans on the ship.

Speaking to Hart van Nederland news show, Harlingen mayor Roel Sluiter called the incident "a terribly tragic accident."