The UN agency said Friday that the practice of singing "Then" met all criteria to merit the recognition.

The practice was "part of the spiritual life of the Tay, Nung and Thai people, reflecting the relationship between man, the natural world and the universe," the agency said.

It also reflects the cultural identity of the groups - from the music to the musical instruments and the dance that accompanies the singing.

The singing of "Then" is a spiritual ritual that seeks peace and happiness for the villages and their people, the UN agency noted.

According to the Department of Cultural Heritage under the Ministry of Culture, Sports and Tourism, the ceremonies associated with this singing follow the journey of a "Then" master, who can be a man or a woman, leading an army of soldiers from the earth to heaven with offerings to the gods, presenting hopes of peace, health and happiness in the New Year.

When the "Then" master begins to sing, the journey begins with the accompaniment of a handmade gourd lute, called "Tinh Tau", which provides background music for the song.

Depending on the purpose of the prayer, the master will make different offerings and prayers in front of the altar. He will use an exorcism sword, bells and other ritual objects to perform the then ceremony.

Usually, the "Then" master, dressed in ceremonial clothing, sings in his particular ethnic language.

The Tay, Thai and Nung ethnic minorities have passed on this longstanding tradition through generations by word of mouth. A "Then" master performs about 200 ceremonies  a year.

The three ethnic groups live primarily in the northeastern provinces of Bac Giang, Bac Kan, Cao Bang, Ha Giang and Lang Son and the northwestern provinces like Dien Bien, Lai Chau and Lao Cai.