Buddhist followers in the central city of Hue, dubbed the country's Buddhist capital, began a week-long celebration of the Buddha's birthday on May 10.
The Buddha's birthday falls on the full-moon day of the fourth lunar month, or May 17.
The provincial Buddhist Sangha lit seven huge floating yellow lotus lanterns on the Perfume River to represent the first seven steps of the Buddha immediately after he was born more than 25 centuries ago.
The lanterns will remain lit up until May 17.
The lighting of the lanterns has become a traditional activity to mark Buddhist celebrations in Hue in recent years.
A week-long exhibition featuring 114 Buddhist artefacts collected by Truong Ngoc Tuong and Tran Dinh Son was also inaugurated on May 10 at the city's Lieu Quan Buddhist Cultural Centre.
The celebration week will feature vegetarian days, concerts, bathing of Buddha idols with scented water, and a procession of a Buddha idol from Dieu De to Tu Dam pagodas.