Viking Line says the M/S Amorella hit the rocks after a power failure on the ship at noon today as it was on its way from the Finnish port of Turku to Stockholm with 1,945 passengers.
In a statement, the operator said a minor leak has been found in a ballast tank but stressed the ship was not taking in water.
The Aland Islands, a group of semi-autonomous Finnish islands, are midway between the two port cities and the ferry was making a scheduled stop there.