The former president of a Tokyo-based consulting firm and two others connected with the company pleaded guilty on Wednesday to bribing officials in Vietnam, Indonesia and Uzbekistan to gain favor for Japanese-funded railway projects in those countries.

Tamio Kakinuma, 65, and the others, former executive Tatsuro Wada, 67, and adviser Koji Ikeda, 58, entered guilty pleas, as did Japan Transportation Consultants Inc. as a company, as the trial opened at the Tokyo District Court.

Prosecutors in their opening statement said the consultancy was solicited for bribes by local officials, with the defendants continuing to provide payments even after a dubious cash transaction by the firm in Vietnam was detected by tax authorities last year, prompting opposition from within the company.

The defendants handed some ¥70 million to three senior officials in Vietnam's state-run railway company between 2009 and 2014 to win favor for an urban railway project in Hanoi funded with Japanese official development assistance, according to the indictment.

The defendants also gave some ¥20 million worth of rebates to five officials in Indonesia's transportation ministry between 2010 and 2013, and some ¥54 million to three officials in Uzbekistan's state-run railway firm between 2012 and 2013.

Japanese tax authorities unveiled the scandal in April 2013 and ordered the company to pay ¥103 million in back taxes.

The Unfair Competition Prevention Law bans Japanese from providing money or other benefits to foreign public servants, with maximum penalties of five years in prison and a fine of ¥5 million.