Russian troops stopped a Ukrainian cargo ship attempting to evacuate Azov battalion leaders from the port of Mariupol on Friday night, Russian Defense Ministry spokesperson Igor Konashenkov revealed Saturday.

Konashenkov also underlined that Kiev had still been attempting to evacuate the leaders of the nationalist Azov battalion, in addition to foreign instructors, from Mariupol.

"On the evening of April 8, Kiev made a new unsuccessful attempt to evacuate the leaders of the Ukrainian Nazis by sea. At night, the Ukrainian cargo ship Apache, registered in Maltese Valletta port, sailing under the Maltese flag, followed a caravan of ships from the Taganrog Bay to the Kerch Strait," the spokesperson detailed.

30 km south-east of the besieged city, the cargo ship abruptly changed course in a bid to break through the Mariupol seaport blocked by the Russian Black Sea Fleet, Konashenkov said.

The cargo ship ignored Russia's calls to communicate, which were transmitted via the international channel, he noted. The Russian troops then opened warning artillery fire at the intruder ship, after which Apache caught fire, prompting its crew to request help and confirm readiness to comply with the orders of Moscow's forces.

No crew members were injured due to the Russian warning shot, and the vessel was escorted to the port of the Russian city of Veysk, the defense official highlighted.

Mariupol has been a playground for crimes committed by the extremist battalion, from killing and torturing Russian prisoners of war to murdering civilians and using them as human shields.

The National Guard of Ukraine's Twitter account had released a video boasting about Azov fighters greasing their bullets with lard to be used against Muslim Chechens on the Russian side. 

Nationalists also faced accusations from Moscow of holding hostages in a maternity hospital in Mariupol, which would not be the first crime committed by the notorious far-right neo-Nazi group, as they opened fire on civilians during their evacuation from the city, killing at least two people and injuring four others.

Russian Ambassador to the United States Anatoly Antonov said Saturday his country would not tolerate Ukrainian troops killing civilians or torturing Russian prisoners of war.

His words came following the publication of videos showing Ukrainian soldiers killing prisoners of war, some of them tied up, as they were lying face down on the pavement, which marked one of many crimes committed by Kiev's forces.

"A video posted online on Monday and verified by The New York Times appears to show a group of Ukrainian soldiers killing captured Russian troops outside a village west of Kyiv," the New York Times said on Thursday.