Here's the claim in the original DM article:
"Last night sources close to Mr Corbyn insisted he was at the service in 2014 to commemorate 47 Palestinians killed in an Israeli air strike on a Tunisian PLO base in 1985.
But on a visit to the cemetery this week, the Daily Mail discovered that the monument to the air strike victims is 15 yards from where Mr Corbyn is pictured – and in a different part of the complex.
Instead he was in front of a plaque that lies beside the graves of Black September members.
The plaque honours three dead men: Salah Khalaf, who founded Black September; his key aide Fakhri al-Omari; and Hayel Abdel-Hamid, PLO chief of security."
According to
this, Fakhri al-Omari was one of the masterminds of the Munich operation.