TOKYO (AFP) - Japan's Prime Minister Shinzo Abe was under mounting pressure Friday (June 16) over allegations that he used his influence to help a friend in a business deal after two official reports appeared to back up the claims.

Abe, in power since late 2012, is in little danger of losing his job, but his popularity has taken a hit in the midst of the latest shady dealings claims.

They come a few months after the conservative premier was forced to deny connections to a controversial director of a school which had purchased government land at a huge discount - and counted Abe's wife as its honorary principal.

This week, the education ministry and Cabinet Office confirmed the existence of documents similar to ones that the opposition pointed to as evidence Abe used his power improperly to pressure bureaucrats into helping a friend.

The claims, originally reported by the Asahi newspaper last month, centre on documents that suggested the education ministry was pressured to grant approval for a new veterinary school run by one of Abe's old university buddies.

The friend, Kotaro Kake, allegedly wanted to open his school in a special economic zone so that he could bypass the ministry's cumbersome regulations.

In response to the claims, the education ministry launched a probe last month but it quickly closed the investigation and said it "could not confirm the existence of the documents".

The ministry flip-flopped a week later, saying the documents did exist.

"I'm taking this result seriously," Education Minister Hirokazu Matsuno told reporters this week.

On Friday, the Cabinet Office also said it had unearthed similar papers, but questioned whether they proved Abe intended to pressure education ministry bureaucrats.

"There was no such instruction from the prime minister," top government spokesman Yoshihide Suga said Friday.

Earlier this year, Abe denied claims he made a donation to the school at the centre of the land scandal.

The school's director Yasunori Kagoike had gained notoriety for operating an Osaka kindergarten that instills pupils with ultra-nationalist views.

A poll by public broadcaster NHK this week showed Abe's government had a 48 per cent support rating, down three percentage points from a month ago. His disapproval rating rose six percentage points in that time frame to 36 per cent, the survey showed.