Two dangling strands of barbed wire have haunted Olaf Hetze for more than a quarter-century, since his failed attempt to escape from the Communist bloc, not by going over the Berlin Wall but around it, by a little-known route through Bulgaria.

Thanks to the work of a German researcher, the full extent of the escape attempts through Bulgaria - and the dangers - is just now coming to light.

At least 4,500 people from various Communist countries tried to flee to the West over the Bulgarian border during the Cold War, said the researcher, Stefan Appelius, a professor of political science at the University of Oldenburg. He estimated that at least 100 of them were killed, but no official investigation has ever been undertaken.