A boy and his twin sisters drowned while trying to catch crabs near their home in Ba Ria Vung Tau on July 22.
The brother, 11, and his 8-year-old sisters went to a rice field with a friend to find crabs. One of the girls fell and slipped into a deep pond.
Her siblings jumped in to rescue her but they all drowned.
Their friend called for help but it was too late.
The bodies were retrieved soon later.
Their father Pham Van Sau said he and his wife work as construction workers and often left their three children at home during summer.
A neighbor said that the children often caught crabs to make their meals or sell the crabs for some money to help their parents.
In related news, two ninth graders drowned on Thursday while swimming in the Vach Bac River in Nghe An Province.
Drowning is common in Vietnam, especially among children even though relevant agencies have warned about the problem for years. About 17 people, mostly children, drown in the country on a daily average, according to WHO.