Japan's National Tax Agency chief, who has been under fire for remarks in parliament about a suspected cronyism scandal that threatens to erode Prime Minister Shinzo Abe's popularity, intends to resign, domestic media said on Friday.

A tax agency spokesman could not confirm the reports by public broadcaster NHK and others that Nobuhisa Sagawa would resign.

Suspicions that a school operator with ties to Abe's wife, Akie, got a sweetheart deal on land for a school in the western city of Osaka helped dent the premier's popularity last year.

Abe has denied that he or his wife did favors for the former head of school operator Moritomo Gakuen, Yasunori Kagoike.

Media said on Friday that Japanese police were investigating as a possible suicide the death of an official at a finance ministry bureau that handled the land deal at the center of the scandal. The official in the western region where the school is located was found dead at his home on Wednesday and police are investigating the matter as a suicide, Kyodo and Jiji news agencies said. A police spokesman declined to comment.

Asked about the reports of the possible suicide, Finance Minister Taro Aso told reporters: "I've heard about the matter."

The former head of the school operator and his wife were arrested in July on suspicion of illegally receiving subsidies.

Abe, in his sixth year in office and eyeing a three-year extension from September, had seemed to put the matter behind him with a big election win for the ruling bloc in October.

But opposition parties have turned up the heat again after the Asahi newspaper said some documents about the land sale might have been doctored.

That followed revelations that the finance ministry had retained documents that officials had said no longer existed. Last year, Sagawa, then the head of the ministry's financial bureau, told parliament the materials had been discarded.

The ministry on Thursday released to parliament hundreds of pages of what it said were copies of the original documents, but opposition lawmakers said their doubts remained.

Aso, a close Abe ally, could end up in the hot seat if it turns out that officials of his ministry altered approved documents.

Abe's ruling bloc has big majorities in both houses of parliament, so his grip on power appears unlikely to be at risk.

But falling support could complicate his bid for a third term as Liberal Democratic Party leader in a September party vote. Re-election would put Abe on track to become Japan's longest-serving premier.