A group representing former Japanese prisoners of war said on Saturday that that documents on some 510,000 Japanese POWs who were interned in the former Soviet Union after the Second World War are stored in a historical materials centre in Moscow, the Japanese news agency Kyodo reported.

Although the documents have been known to exist, Saturday's announcement was the first claim about the number of POWs involved, the Tokyo-based group said.

The Japanese Health and Welfare Ministry estimates that 575,000 Japanese worked in labour camps in Siberia and other parts of the former Soviet Union.

Russia and Kazakhstan have handed over to Japan the names of 40,025 POWs who died during internment.

The Russian government, which pledged in a bilateral agreement in 1991 to hand over the names of all Japanese internees, told the group that the documents on the 510,000 POWs related to those who survived internment.

A senior Health and Welfare Ministry official said he hoped the documents would be handed over soon in accordance with the bilateral pact, Kyodo reported.

BBC Monitoring (http://www.monitor.bbc.co.uk), based in Caversham in southern England, selects and translates information from radio, television, press, news agencies and the Internet from 150 countries in more than 70 languages.