A former concentration camp guard, now aged 100, will stand trial accused of complicity in 3,518 murders, German public prosecutors have announced. 

The prosecutor's office in Neuruppin said a medical assessment confirmed the man was "fit to stand trial," with hearings limited to two-and-a-half hours per day.

The man, who has not been named, is accused of "knowingly and willingly" assisting in the murder of prisoners at the Sachsenhausen camp, north of Berlin, between 1942 and 1945.

He is accused of complicity in the "execution by firing squad of Soviet prisoners of war in 1942" and the murder of prisoners "using the poisonous gas Zyklon B."

Lawyer for some of the victims, Thomas Walther, told the German newspaper Welt am Sonntag: "Several of the co-complainants are just as old as the accused and expect justice to be done."