"My thoughts go out to the family and their loved ones. This is so heartbreaking," Kristersson writes on Instagram.
He also thanks those who have taken part and are still taking part in the search, the Swedish Sea Rescue Society, the Coast Guard, the police and volunteers, and especially mentions the couple who acted when they heard the distress call and rescued the father and son from the water.
"Individual brave people with their hearts in the right place can work wonders when seconds count," the Prime Minister writes.
