KYIV, Aug 21 (AFP) - Russia might take the provocative step of putting Ukrainian soldiers on trial as Kyiv marks 31 years of independence for the war-ravaged country next week, Ukraine's President Volodymyr Zelenskyy warned on Sunday (Aug 22).

Zelenskyy cited media reports that Russia was preparing to put Ukrainian fighters captured during the siege of Mariupol on a public trial to coincide with the independence anniversary on Wednesday.

Ukraine's Independence Day, Aug 24, will also mark six months since Russia invaded the former Soviet republic, in a devastating war that has cost thousands of lives.

"If this despicable court takes place, if our people are brought into these settings in violation of all agreements, all international rules, there will be abuse," Zelenskyy warned in an evening address.

"This will be the line beyond which no negotiations are possible."

The capital Kyiv has already announced a ban on public gatherings. Kharkiv too, declared a curfew around the holiday.

Zelenskyy was returning to a subject he had already raised in the previous night's remarks.

"Russia could try to do something particularly disgusting, particularly cruel," he warned late on Saturday.

"One of the key objectives of the enemy is to humiliate us," and "to sow despondency, fear and conflict".

But he added: "We have to be strong enough to resist all provocation" and "make the occupiers pay for their terror".