"Do not use any plastic materials during lantern flower festivals to avoid causing pollution and destroying the water environment," the sangha said in a statement sent to its all localities last week.

The statement has come as a response to many Buddhist followers who used plastic materials to make flower lanterns or placing a small plastic cup in the paper lanterns before putting a candle inside.

A Buddhist event held in August had sparked environmental controversy for releasing 30,000 plastic lanterns to the sea off the northern city of Hai Phong.

Several days after the festival, photos were posted on the internet showing large numbers of plastic lanterns floating on Lan Ha Bay, drawing criticism and anger over posing a serious environmental hazard to marine life.

Local authorities, however, said later that they had collected all the plastic lanterns right after the festival and that the photos being circulated online were old ones. It was publicly confirmed later that all plastic lanterns had indeed been removed from the bay, but the question about the practice itself remained unsolved.

The floating of flower lanterns are a longstanding Buddhist tradition usually done on special events. The ritual involves floating lit flower lanterns, which for years had been made of paper, along rivers and other waterways.

Apart from not using any plastic in the lantern, the sangha has also asked followers to "fight against plastic waste" in response to the a national campaign to achieve zero use of disposable plastic in urban shops, markets and supermarkets by 2021 and nationwide by 2025.

Followers should switch from single-use plastic products to those made of paper, cloth or other materials that can be reused many times, the sangha statement said.

Buddhism is the most popular religion in Vietnam, with nearly 45 million followers.

Vietnamese per capita plastic waste is the third highest in Southeast Asia, increasing from 3.8 kilograms in 1990 to 41.3 kilograms in 2018, according to a survey released last week by Ipsos Business Consulting, a global growth strategy consulting firm based in Paris.