One of the top people on the most-wanted list of Nazis has been declared unfit for trial by prosecutors in Germany.

They said former SS lieutenant Gerhard Sommer, 93, had severe dementia. He is one of 10 ex-Nazi officers found guilty in absentia in Italy of one of the country's worst civilian wartime massacres, the murder of 560 civilians in the Tuscan village of Sant'Anna di Stazzema in August 1944.

The Nazis, retreating in northern Italy ahead of Allied troops, surrounded the village early on 12 August and in the space of a few hours murdered men, women and 119 children.

Sommer was serving at the time in an SS Panzer division. He now lives in a nursing home in Hamburg-Volksdorf and tops the Simon Wiesenthal Center's list of most-wanted Nazi criminals.

Hamburg lawyer Gabriele Heinecke, who has campaigned on behalf of the victims' families to put him on trial, was asked by Berlin website Tageszeitung if she thought dementia could be faked. She said: "Of course. In matters of pensions it's something that happens every day."

For years, attempts have been made to put Sommer on trial. German prosecutors were confident that if he had been deemed fit, Sommer would "with high probability have been charged with 342 cases of murder, committed cruelly and on base motives".

The decision to drop the trial comes as Oskar Groening, another 93-year-old former Nazi, described as "The Bookkeeper of Auschwitz" is being tried in Germany on at least 300,000 counts of accessory to murder.