Many people are feared dead after two helicopters carrying a total of five collided mid-air and crashed to the ground.
According to Finland police, the exact number of victims and the identities of the passengers are still being determined.
From several media reports, the helicopters took off from Estonia and were carrying businessmen, with three people in one and two in the other.
Reports said the helicopters collided west of the capital Helsinki around midday.
However, officials are yet to give indication of what led to the collision.
As Finnish newspaper Iltalehti reports, a witness, identified as Antti Marjanen, said they saw one of the helicopters hit the other during a manoeuvre.
“One of them dropped like a stone and the other one more slowly. I didn’t hear any sound,” Marjanen was quoted as saying.