TOKYO, March 27 (Xinhua) -- A former senior bureaucrat on Tuesday denied under oath that Prime Minister Shinzo Abe, his wife Akie, or other politicians were involved in any way with the tampering of documents regarding the cut-price sale of state land to a nationalist school operator.

Despite the denial however, the opposition camp and the public, bemused and outraged by the protracted cronyism scandal, are livid at the ruling camp seemingly trying to force the scandal to an end by pinning the blame on the Financial Bureau and a senior finance ministry official.

The opposition camp henceforth are eying to summon Akie Abe and other senior politicians to give testimony while Osaka-based prosecutors are stepping up their investigations into the matter and getting information pertinent to the ordering of the document alterations, sources with knowledge of the matter said Tuesday.

During sworn testimony given earlier in the day to the House of Councillors' Budget Committee, former national tax agency head Nobuhisa Sagawa admitted that the papers were altered within his section but maintained there was no pressure from the outside, including from the prime minister, his wife, Finance Minister Taro Aso, or any other senior officials to amend the documents.

Sagawa, 60, who resigned this month as head of the National Tax Agency where he was previously in charge of the state land sale, refused however to testify on a number of pressing points, including exactly how the ministry's Financial Bureau had deliberately altered the documents, or when he personally became aware of the falsification.

But Sagawa's refusal to answer numerous questions by stating that as the case is currently subject to prosecutors' investigation so that he could face possible criminal prosecution, meant that the bureaucrat did little to advance the proceedings, which irked both opposition and some members from within the ruling camp.

However, Sagawa apologized for causing disruption in the Diet and for undermining trust in the administration.

He also said that as head of the bureau at the time, he bears all the responsibility for the document alterations.

Prosecutors in Osaka have also been interviewing Finance Ministry officials at their own volition as part of a broader probe into the document-tampering scandal.

According to Japan's public broadcaster NHK, the prosecutors in question may have knowledge of an e-mail sent by a Financial Bureau official to the Ministry's Osaka bureau, ordering the documents be falsified.

If Sagawa ordered the falsifications, he could be charged with creating false public documents, NHK said of the matter.

The opposition camp, for its part, on Tuesday tried to ascertain whether the huge discount and subsequent document tampering was due to political pressure, like that from a senior politician or official like Aso, or whether they were altered voluntarily out of consideration for the prime minister's office and his wife's involvement with the school operator.

Abe, Akie and Aso have all denied their involvement and any wrongdoing in the prolonged influence-peddling scandal.