The accident happened in the mountainous province at around 2 p.m. A group of six students in Bat Xat District went for a swim in the stream, which is seven to ten meters deep, and hidden behind bamboo thickets.

Unfortunately, the school girls fell into a deep water hole and only two of them managed to swim to the shore.

The bodies of the four students were recovered at around 3 p.m.

"This morning was the last class of the school year and they didn’t have to go to class in the afternoon," a local official said.

Child drowning deaths are not uncommon in Vietnam. More than 11,000 children drown each year, according to a recent survey by the World Health Organization.

The rate of child drowning in Vietnam is higher than other Southeast Asian nations and 10 times higher than that of developed countries, the survey said.

On Monday, four students from the central province of Khanh Hoa, home to the famous beach resort town of Nha Trang, drowned in a local river.

Last month, eight primary and secondary school boys in Hoa Binh, northern Vietnam, drowned in a local river.

Bloomberg Philanthropies (BP) had last year announced a $2.4 million donation to fund the first two years of a five-year program to prevent drowning deaths among children in Vietnam.