MOSCOW (Reuters) - Russian mercenary leader Yevgeny Prigozhin remains under investigation by the Federal Security Service (FSB) on suspicion of organising an armed mutiny, the Kommersant newspaper reported on Monday, citing an unidentified source.

The criminal case against Prigozhin was initiated on June 23 after he announced a "march for justice" by his fighters against the military leadership, who he said were cowards who were undermining Russia's war effort in Ukraine.

As part of a deal, as set out by the Kremlin's spokesman, criminal charges against the mutineers were to be dropped in exchange for their return to camps, and Prigozhin was to move to Belarus.

On its website, Kommersant cited its source as saying there had not yet been time to change the status of the case.

(Reporting by Guy Faulconbridge; Editing by Kevin Liffey)