Chairman of Hai Ninh Ward People's Committee, Le Dinh Phuong announced on Sunday evening that the tragic accident occurred at 3 pm the same day when a local man Mai Viet Tu, 62, took his four grandchildren to swim at the Hai Ninh Beach.
After a while, he took the youngest child home, leaving three others including two boys and a girl aged between 11 and 14 at the beach.
The grandfather then returned to the beach to call the children but could not find them.
Rescue forces were sent to search for the children and they found three bodies of the children some 500 metres from the beach at 5pm.
"The water was calm today but maybe the children went far away from the shore and were swept out to sea," the official said.
Local people usually go to Hai Ninh Beach to swim during the summer, although this beach has no rescue staff available.
