Russia's Supreme Court on Wednesday postponed for the second time a hearing on whether to designate Ukraine's Azov Regiment, which defied besieging Russian forces for weeks in Mariupol, as a terrorist entity.
A court official said the hearing, first set for May 26, had now been rescheduled for Aug. 2. No reason was given.
Russia said in May that 2,439 Ukrainian defenders had surrendered after staging a desperate last stand in the bunkers and tunnels of the Azovstal steelworks in the southern port city, scene of some of the worst devastation of the war.
They included members of the Azov Regiment, whose fighters are revered as heroes in Ukraine but have frequently been characterised by Moscow as Russian-hating neo-Nazis.
The unit was formed in 2014 as an extreme right-wing volunteer militia to fight Russian-backed separatists, but was subsequently folded into the Ukrainian National Guard. Ukraine says it has been reformed away from its radical nationalist origins and is now apolitical.
It has been a special focus of Russian hatred in a war that President Vladimir Putin has cast as a "special military operation" to demilitarise and "denazify" Ukraine - a justification dismissed by Kyiv and the West as a baseless pretext for invasion.
Relatives of the Ukrainian fighters have appealed for their rights to be protected under the 1949 Geneva Conventions on the conduct of war, and Ukraine says it expects them to be exchanged for Russian prisoners-of-war.
But if the Supreme Court designates the Azov Regiment as a terrorist entity, it could pave the way for some of the men to face trial, as members of the Russian parliament have demanded.
Organising terrorist activity is punishable with life imprisonment in Russia. Participating in a terrorist organisation carries a prison sentence of 10 to 20 years.
The whereabouts of the surrendered Mariupol defenders is unclear. Russian state news agency Tass said on June 7 that more than 1,000 of the men had been transferred to Russia for investigation.
Russia's justice ministry, prison service and Investigative Committee did not immediately reply to requests for information about the men's location and legal status.
Under the third Geneva Convention, prisoners of war should be humanely treated and be released and repatriated without delay after the cessation of active hostilities.
(Reporting by Mark Trevelyan; editing by John Stonestreet)
