The event was also held to call for entry for the 47th edition of the competition, launched by the Universal Post Union (UPU) in 1971.
Vietnam became an UPU official member in 1976 and submitted its first entries to the competition in 1987.
Each year, the UPU International Bureau selects a theme for the competition, aiming to encourage literacy in children and young people and develop their ability to express their thoughts clearly.
Millions of Vietnamese students have sent their letters to the UPU competition at the national and international levels over the past three decades. Vietnam has won 13 international prizes, including three first, one second and three third prizes.
This year, Nguyen Do Huyen Vi, an eighth grader from Tay Son Secondary School in Hai Chau district, central Da Nang city, won the first prize at the national level and the consolation prize at the international level for her letter to the UN Secretary-General, advising him on how to solve the Syrian refugee issues.