Immigration authorities are clamping down on applications for student visas in an apparent bid to staunch the flow of individuals who abuse the system simply to work.

Although immigration officials deny they are targeting certain nations, particularly those in Southeast and South Asia, statistics released by the Tokyo Regional Immigration Bureau point to sharp declines in the percentages of successful applications from those regions.

Justice Ministry figures show there were about 310,000 foreign nationals in Japan on student visas as of the end of 2017. That represents an increase of about 100,000 from five years ago.

The clampdown comes as the government moves to push through legislation that would establish a new residence status for foreign workers considered to have specific skills. If that new status is implemented as the government hopes from next April, there may well be a further decline in foreign nationals coming to Japan to study.

Because many Japanese language and other schools regularly allow in new students mainly in April and October, applications tend to concentrate in the preceding months.

According to documents the Tokyo Regional Immigration Bureau distributed to Japanese language schools, there were 29,801 applications for student visas for the April term, and 77.7 percent were approved.

However for the October term, only 65.6 percent of the 16,495 applications were approved.

And while applicants from China, Vietnam and South Korea were approved at rates hovering around 90 percent, the situation was markedly different for applicants from Southeast and South Asia.

The approval rate for applicants from Nepal plunged from about 48 percent to around 8 percent, while the figure for Sri Lanka fell from about 51 percent to just 3 percent. The approval rate for Bangladesh dropped from about 58 percent to about 3 percent, while that for Myanmar fell from about 74 percent to about 20 percent.

Sources said a similar trend in approval rates was evident at the other regional immigration bureaus around Japan.

Tokyo Regional Immigration Bureau officials admit they have become more stringent in their assessment of applications, given that some students have been found to be working beyond the stated hours defined by law.

In submitting applications, individuals are required to include documents that certify their Japanese language ability and the means to pay for tuition once in Japan. Sources said there have been cases of documents being falsified for student visa application screening.

The stricter rules have caused problems for a number of Japanese language schools in Tokyo as enrollment numbers have fallen.

"In the 10 or so years since starting this school, the approval rate even at the lowest level had been 50 percent," said the head of one school in the greater Tokyo metropolitan area. "I have no idea what is the basis for the new decisions."

The school had planned to welcome 20 or so students from Nepal and Sri Lanka from the October term, but none of the applicants were given visas.

Immigration authorities said the decisions were not made based on nationality when the school sought an explanation. No further details were provided.

School officials said they made extensive efforts to ensure that prospective students had the financial resources to attend classes.

There have been cases of individuals taking out loans to inflate their savings account balance and withdrawing the money after the certificate of the balance was submitted for the visa application.

For their part, school officials have interviewed prospective students and visited local banks to check on their financial situation.

Other school operators view the tighter vetting process as simply an attempt to put things back on a more even keel.

One operator noted there have been cases in the recent past of financially strapped individuals coming to Japan ostensibly to study, only to work illegally.

An official with the Association for the Promotion of Japanese Language Education, noting that schools have made efforts to prevent such illegal labor practices, called the last move "simply too drastic."

(This article was written by Ryo Takano and Kazumichi Kubota.)