A prosecutor has accused a Ukrainian man of plotting a terror attack against the Russian Embassy in London after returning from a visit to eastern Ukraine at the height of the conflict there.

Prosecutor Robin Sellars told the Central Criminal Court that 35-year-old Vadim Bezkorovainiy carried out extensive research online to promote "his political motive."

Authorities say he went on three reconnaissance missions to the embassy from his home in Luton, southeast England, where police found images and video files suggesting he was plotting a terror attack.

The conflict between government forces and Russia-backed rebels in eastern Ukraine has claimed more than 8,000 lives since it began in April 2014.

Bezkorovainiy is charged with preparation for acts of terrorism between January and March last year.

He has denied the charge.