A White House spokesperson expressed alarm about two captured American fighters who could face the death penalty in the newly independent Donetsk Peoples' Republic.
John Kirby, the coordinator for Strategic Communications at the National Security Council in the White House, told reporters on Tuesday that it is “appalling” that Kremlin spokesman Dmitry Peskov would even suggest such a possibility for the Americans.
“It's appalling that a public official in Russia would even suggest the death penalty for two American citizens that were in Ukraine. And we're going to continue to try and learn what we can about this,” Kirby said.
Russia said last week that two Americans were captured while fighting with Ukraine's military.
Peskov called them "mercenaries" who were engaged in illegal activities and should be "held accountable for those crimes.”
Peskov said the detained men are not covered by the Geneva Conventions as they are not regular troops.
"They're soldiers of fortune and they were involved in illegal activities on the territory of Ukraine. They were involved in firing and shelling our military personnel. They were endangering their lives," he said.
According to the Interfax news agency, the two Americans were currently in the Russian-backed separatist region of Donetsk in eastern Ukraine.
The two men have been identified as Andy Huynh and Alexander Drueke, both from Alabama. Britons Shaun Pinner and Aiden Aslin and Morrocan citizens.
Last Friday, Drueke and Huynh were shown alive and in a detention facility in Donetsk, where a court on June 9 convicted two Britons and a Moroccan for being mercenaries and sentenced them to death.
Asked about them by NBC News on Monday, Peskov called Drueke and Huynh “soldiers of fortune” who were involved in “illegal activities” and fired on Russian troops, and said their fate would “depend on the investigation” and the subsequent trial.
“Either way, it’s equally alarming, whether they actually mean what they're saying here and this could be an outcome, that they could levy a death penalty against two Americans in Ukraine,” Kirby said on Tuesday.
“Or that they just feel it's a responsible thing for a major power to do, to talk about doing this as a way of signaling to the president of the United States and the American people,” he added.
Earlier on Tuesday, the US Department of State confirmed a second American citizen has died while fighting against Russians in Ukraine.
A State Department official said US citizen Stephen Zabielski of Hernando, Florida, died in Ukraine, without offering any further details.
State Department officials “have been in touch with the family and have provided all possible consular assistance,” the official added.
A local news outlet The Recorder published the obituary of Zabielski, 52, who it said died while fighting in the village of Dorozhniank.
He is formerly of Cranesville, New York and “enjoyed life.”
Ukraine has been at war with Russia since President Vladimir Putin declared a military operation in the neighboring country in late February, following Kiev’s failure to implement the terms of the Minsk agreements and Moscow’s recognition of the breakaway regions of Donetsk and Luhansk.