A counter-terrorism operation in January involving several European countries came close to capturing the man suspected of organising last month's Paris attacks, the BBC reports.
Greek police tried to arrest Abdelhamid Abaaoud as he was directing a Belgian terror cell via phone from Athens, but the operation failed.
The reasons remain unclear, but it's believed there may have been a failed attempt to monitor Abaaoud in a public square by tracing his mobile phone signal.
Abaaoud died in a battle with French police last month, just days after a string of attacks in Paris that killed 130 people.
According to the BBC, the operation aimed to target Abaaoud before a raid was carried out by security forces in the Belgian municipality of Verviers on January 15.
That raid went ahead, resulting in the deaths of two suspected jihadists.
Greek police eventually raided two flats, where an Algerian man was extradited to Belgium.
DNA evidence shows Abaaoud had been in both flats at one stage. A neighbour in the block, Vasilis Katsanos, said he had seen Abaaoud nearby on at least two occasions.
It's also known that Salah Abdeslam, a Paris attacker who remains on the run, had travelled to Greece in August where he stayed for three days.
And two of the suicide bombers who attacked the Stade de France had posed as refugees, as they crossed by boat from Turkey to the island of Leros in October.
