Two British citizens and a Moroccan were sentenced to death Thursday for fighting on Ukraine's side, in a punishment handed down by the country's pro-Moscow rebels.

The proceedings against the three captured fighters were denounced by Ukraine and the West as a sham and a violation of the rules of war.

Meanwhile, as the Kremlin’s forces continued a grinding war of attrition in the east, Russian President Vladimir Putin appeared to liken his actions to those of Peter the Great in the 18th century and said the country needs to “take back” historic Russian lands.

A court in the self-proclaimed Donetsk People’s Republic in Ukraine found the three fighters guilty of seeking the violent overthrow of power, an offense punishable by death in the unrecognized eastern republic. The men were also convicted of mercenary activities and terrorism.

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Russia’s state news agency RIA Novosti reported that the defendants — identified as Aiden Aslin, Shaun Pinner and Brahim Saadoun — will face a firing squad. They have a month to appeal.

The separatist side argued that the three were “mercenaries” not entitled to the usual protections accorded prisoners of war. They are the first foreign fighters sentenced by Ukraine’s Russian-backed rebels.

Ukrainian Foreign Ministry spokesman Oleh Nikolenko condemned the proceedings as legally invalid, saying, “Such show trials put the interests of propaganda above the law and morality.” He said that all foreign citizens fighting as part of Ukraine’s armed forces should be considered Ukrainian military personnel and protected as such.

British Foreign Secretary Luz Truss pronounced the sentencing a "sham judgment with absolutely no legitimacy.” Prime Minister Boris Johnson’s spokesman Jamie Davies said that under the Geneva Conventions, POWs are entitled to immunity as combatants.

Saadoun's father, Taher Saadoun, told the Moroccan online Arab-language newspaper Madar 21 that his son is not a mercenary and that he holds Ukrainian citizenship.

Aslin’s and Pinner’s families have said that the two men were long-serving members of the Ukrainian military. Both are said to have lived in Ukraine since 2018.

The three men fought alongside Ukrainian troops before Pinner and Aslin surrendered to pro-Russian forces in the southern port of Mariupol in mid-April and Saadoun was captured in mid-March in the eastern city of Volnovakha.

Another British fighter taken prisoner by the pro-Russian forces, Andrew Hill, is awaiting trial.

The Russian military has argued that foreign mercenaries fighting on Ukraine’s side are not combatants and should expect long prison terms, at best, if captured.

In other developments, Putin drew parallels between Peter the Great's founding of St. Petersburg and modern-day Russia's ambitions.

When the czar founded the new capital, “no European country recognized it as Russia. Everybody recognized it as Sweden,” Putin said. He added: “What was (Peter) doing? Taking back and reinforcing. That’s what he did. And it looks like it fell on us to take back and reinforce as well.”

Putin also appeared to leave the door open for further Russian territorial expansion.

Also read: Russian missiles strike Kyiv, shattering sense of calm

“It’s impossible — Do you understand? — impossible to build a fence around a country like Russia. And we do not intend to build that fence,” the Russian leader said.

In other developments, French President Emmanuel Macron told Ukrainian President Volodymyr Zelenskyy that France was ready to send more “heavy weapons” to Ukraine, according to Macron’s office. French officials did not elaborate on the weaponry. The phone conversation came after Macron angered Ukrainian officials by saying world powers should not “humiliate” Putin.”

Zelenskyy said the Ukrainian army continued to push Russian forces back from Kharkiv, the country's second-largest city, which lies to the north of the Donbas. The transmission of Ukrainian television was restored after a TV tower was shelled.

“Hitting television centers, destroying communication channels, leaving people isolated – this is the tactic of the occupiers that they cannot do without, for openness and honesty also are weapons against all that the Russian state does,” he said late Thursday in his evening address.