TOKYO - Japan has acknowledged that Allied prisoners of war were put to work in a coal mine owned by Prime Minister Taro Aso's family, reversing previous denials, after newly found documents provided proof.

The Health and Welfare Ministry said yesterday that the wartime documents showed that 300 British, Dutch and Australian prisoners worked at the Aso family mine in Fukuoka, southern Japan, from April 1945 through Japan's surrender four months later. It was the first time the government had acknowledged the use of prisoners at an Aso mine.

Two Australian POWs died at the mine, according to a government official who verified the authenticity of the documents.

The disclosure could deal a further blow to the embattled prime minister, whose approval rating has plunged to about 20 percent in just three months since he took office. Aso has repeatedly come under fire for gaffes and for lack of leadership through the global economic crisis.

The acknowledgment of the Aso wartime legacy came in response to questions submitted last month by opposition lawmaker Yukihisa Fujita, along with a copy of the documents, which contained records from the prison camp at the mine. Fujita demanded that the government verify their authenticity and the use of Allied POWs at Aso's family mine - a practice the government has long denied.

Aso has kept mum over the latest embarrassment. Earlier this year, he distanced himself from revelations in other wartime documents that Korean forced laborers were used at his grandfather's mine.

"I was only 5 at the time, and I have no personal memory of that," Aso said at the time. Aso briefly served as president of the family company - now called the Aso Group - before becoming a lawmaker.

Health and Welfare Ministry official Katsura Oikawa confirmed Thursday that the 43 pages of documents that Fujita submitted - after they were found in the ministry storage - were genuine. Oikawa told a parliamentary committee that the documents had been overlooked for decades because the government had put little effort into examining wartime records.

Japan has acknowledged it used prisoners for forced labor in mines, shipyards and jungles during World War II.

"Many other mining companies had used such prisoners as laborers," said Hiroshi Kawahara, a political scientist at Tokyo's Waseda University. "And the latest revelation could trigger a wider probe into Japan's treatment of prisoners during the war."