Nguyen Van Hieu was dismissed from the state-owned Vietnam Railways Corporation, Tuoi Tre newspaper reported, after allegations in Japanese media that it took bribes over an urban railway project in Hanoi.
The Yomiuri Shimbun newspaper reported on Friday that the president of Japan Transportation Consultants had admitted paying more than US$780,000 (Bt25.2 million) for the railway project, which is worth over $41 million in Japanese overseas development assistance (ODA).
Japan is the largest donor of aid to the Southeast Asian country, providing more than $1.1 billion in 2013.
Tokyo leaves it up to Vietnamese authorities to select providers for the related goods and services, leaving Japanese companies to compete for the lucrative contracts.
In 2008, Japan arrested four Tokyo-based consultants for allegedly bribing officials in Ho Chi Minh City for a flyover project, also funded by Japanese aid, leading to a temporary suspension of aid.
Tuoi Tre reported allegations that Japan Transportation Consultants also paid civil servants in Indonesia and Uzbekistan bribes more than $1.27 million between 2008 and 2012 for contracts connected to five Japan-funded projects.
A conviction for bribery in Vietnam can carry the death sentence.