Paul Whelan
© Sputnik / Ilya Pitalev
Paul Whelan during a court hearing
Russian prosecutors demanded an 18-year prison term for former US marine Paul Whelan, on charges of spying for Western intelligence, on the last day of his trial in Moscow.

The Canadian-born defendant, who holds passports of four countries, was arrested in Moscow in late 2018 after reportedly receiving a flash drive with classified material from a Russian acquaintance. His attorney insists Whelan is innocent.

In his final statement to the court, the 50-year-old reiterated that he was not a spy and asked for an acquittal, according to the Moscow city court press service.

Prosecutors believe they have a strong case, and are pushing for Whelan to serve time in a high-security facility.

The trial is being conducted behind closed doors, and has received less Western media coverage than previous espionage cases involving Russia and the US. The court is expected to hand down its ruling in mid-June.

Whelan has been a regular visitor to Russia since the mid-2000s, and was reportedly red-flagged as a possible intelligence asset several years before his arrest.

His defense team claims he is the victim of a frame-up, and that Whelan believed he was receiving a USB thumb drive with photos from a joint event from a friend, when he was detained.

Whelan served as a US marine, and was discharged after being court-martialed for attempted fraud. His family say his unusual collection of citizenships - he holds passports of the US, the UK, Canada and Ireland - are due to a personal quirk.