OITA , Japan, June 5 (Reuters) - Bank of Japan board member Takehiro Sato said on Thursday the disinflationary trend now appearing in the euro area may be prolonged, mainly in peripheral countries.

"The European Central Bank has already revealed its policy stance that it will not hesitate to make use of unconventional measures to address the risk of prolonged disinflation," Sato said in a speech to business leaders in Oita, southern Japan.

"I therefore am keeping a watchful eye on its future conduct of monetary policy," he said.

(Reporting by Leika Kihara; Editing by Chris Gallagher)