Indonesian Vice President Boediono has said he was questioned as a witness by anti-graft investigators over a controversial bank bailout, in a case that could prove problematic for the government ahead of polls next year.

The case centres on a 6.76 trillion rupiah ($584 million) government bailout of small lender Bank Century at the onset of the financial crisis in 2008.

The total amount paid out to save the bank was far higher than the initial proposal of just 680 billion rupiah, and bailout money was allegedly siphoned off by well-connected depositors.

The case rocked the government of President Susilo Bambang Yudhoyono and renewed attention on it comes as his beleaguered party seeks to claw back popularity ahead of elections in 2014 following a string of corruption scandals.

Boediono was central bank governor at the time of the bailout and along with other top officials, including then finance minister Sri Mulyani Indrawati, authorised the bank rescue.

Indrawati now works for the World Bank in Washington and was questioned over the case earlier this year as a witness.

The vice president, who like many Indonesians goes by on name, said late Saturday that he was questioned by investigators from the Corruption Eradication Commission (KPK) for 10 hours that same day as a witness in the case.

"The focus was on a short-term loan facility," said Boediono, who himself is not a member of any political party.

"There were many questions which I answered as thoroughly as I could, from the early stages until after the bailout," he said.

He did not provide details, saying that they "would disturb the law enforcement process".

Defending the move, he told reporters the period was "very explosive".

"I can only say that I had carried out my responsibility with all sincerity, with the aim of contributing the best for the nation in the face of extraordinary challenges," he said.

Boediono's questioning followed the detention of former central bank deputy governor, Budi Mulya, last week by the KPK for his role in the same case. He has been named a suspect in the case.