Japan has acknowledged that it conducted only a limited investigation before claiming there was no official evidence that its imperial troops coerced Asian women into sexual slavery before and during World War II.

A parliamentary statement signed Tuesday by Prime Minister Shinzo Abe acknowledged the government had a set of documents produced by a postwar international military tribunal containing testimony by Japanese soldiers about abducting Chinese women as military sex slaves. That evidence apparently was not included in Japan's only investigation of the issue, in 1991-1993.

Tuesday's parliamentary statement also said documents showing forcible sex slavery may still exist. The statement did not say whether the government plans to consider the documents as evidence showing that troops had coerced women into sexual slavery.

Over the past two days, top officials of Abe's conservative government have appeared to soften their stance on Japan's past apologies to neighboring countries for wartime atrocities committed by the Imperial Army, saying Japan does not plan to revise them.

The backtracking appears intended to allay criticisms of Abe's earlier vows to revise the apologies, including an acknowledgment of sexual slavery during the war, and calm tensions with neighbors South Korea and China. The U.S. government also has raised concerns about Abe's nationalist agenda.

Abe has acknowledged so-called “comfort women” existed but denied they were coerced into prostitution, citing a lack of official evidence. He also has repeatedly vowed to reassess apologies by past Japanese administrations.

The parliamentary statement, released Tuesday and seen by the Associated Press on Wednesday, was in response to an official inquiry last month to the upper house of Parliament by opposition lawmaker Tomoko Kami, who said the government's investigation into sex slavery was “insufficient” and documents it claimed to have collected were incomplete.

Kami, of the Japan Communist Party, also asked whether the government had ever updated its archives to reflect more recent findings than the earlier investigation. The answer was no.

The statement acknowledged documents produced by the 1946-1948 International Military Tribunal for the Far East, held in Tokyo, but said they were not in the Cabinet Secretariat's archives. It did not say when the documents were found or whether they are reflected in any official statements about sexual slavery.

Abe also has criticized the tribunal's decisions as “condemnation by the allied victors' judgment,” but has said he's in no position to object to the rulings Japan had already accepted.

The parliamentary statement described the 1993 findings as “the result of an all-out and sincere investigation” that brought “closure.” But it said the government is open to updates if new findings are valid.

“Due to the nature of the issue, there is a possibility that previously unavailable documents may be discovered. In such a case, we are asking related ministries and offices to report to the Cabinet,” it said.

The documents quote testimony from Japanese soldiers saying they recruited women by posting advertisements for factory workers and “threatened them and used them as prostitutes for the bestial lust of the troops.” 

One army lieutenant testified that he helped set up a brothel for soldiers including himself, forcing five women in the city of Guilin in southern China to work as prostitutes for eight months.

Meanwhile, Chief Cabinet Secretary Yoshihide Suga said Wednesday that Japan recognizes the harm it caused during its invasion and occupation of much of Asia, and that it has repeatedly and clearly stated that position.

“The Abe government has expressed sincere condolences to all victims of the war, in and out of the country, and there is no change in that,” Suga said in response to a question about a comment by South Korean President Park Geun-hye, published in The Washington Post this week, asserting that Japan should correct its view of its wartime history.

Foreign Minister Fumio Kishida echoed Suga's remarks.

“The Japanese government has accepted the facts of history in a spirit of humility, expressed once again our feelings of deep remorse and our heartfelt apology, and expressed our feelings of profound mourning for all victims, both at home and abroad,” he told reporters. “And Prime Minister Abe shares the same view.”

China and South Korea have reacted harshly to recent nationalistic events and remarks, including visits by several Japanese government ministers and nearly 170 lawmakers to Tokyo's Yasukuni Shrine, which memorializes 2.3 million war dead, including 14 wartime leaders convicted of war crimes. Rancor over territorial disputes has further strained relations between Japan and its neighbors.

Only in the past two decades has Japan acknowledged some of its past brutalities, including medical atrocities and use of poison gas, as well as sexual slavery _ a legacy that still haunts Tokyo's relations with its neighbors.

Before he took office in December, Abe had advocated revising a 1993 statement by then-Prime Minister Yohei Kono expressing remorse for the suffering caused to the sexual slaves of Japanese troops. (AP)