The files contain personal data on millions of the Nazis' victims

The electronic transfer is part of an agreement to open up the Bad Arolsen archive, overseen by the International Committee of the Red Cross (ICRC).

The files, kept in Germany, were found in concentration camps and other Nazi prisons at the end of World War II.

Several countries have not yet ratified the agreement, delaying full access.

The archive will only be fully opened to the public when the 2006 protocol is ratified by Italy, France and Greece. That is expected later this year.

The ICRC says the archive has now transferred many documents from the archive to the Holocaust Memorial Museum in the US and to the Yad Vashem Holocaust Centre in Israel.

Chilling details

The 47 million files stored in the spa town of Bad Arolsen hold meticulously recorded information on forced labourers, concentration camp victims and political prisoners. They take up 26km (16 miles) of shelving.

Historians believe many more details about the Nazis' murder and brutal exploitation of millions of Jews, Roma (Gypsies) and other victims will be revealed.

"After a long political process, we can now give researchers and the public access to the files," said Reto Meister, director of the ICRC's International Tracing Service (ITS).

So far, 12 million documents have been digitised for electronic transfer, the ICRC says.

In grey, bureaucratic language the Nazis kept records on the smallest details - from the number of lice on a prisoner's head to the exact moment of their execution.

The archive has been used to help people trace their relatives. But access has been restricted to protect victims' privacy.

The archive is controlled by an 11-nation treaty signed in 1955 and amended by the 2006 protocol. The countries are: Belgium, Britain, France, Germany, Greece, Israel, Italy, Luxembourg, the Netherlands, Poland and the US.