Russia has not ruled out that the American citizens captured in Ukraine could face the death penalty, even as it said Tueday they were subject to court decisions.


"We can't rule anything out, because these are court decisions. We don't comment on them and have no right to interfere," a Reuters report quoted Kremlin spokesperson Dmitry Peskov as telling reporters.


With the families of these Americans saying they had not returned from a mission around the Kharkiv region in Ukraine, the Kremlin said it did not know where the men were now.


Russia had said on Monday the two Americans detained in Ukraine were mercenaries, adding that they were not covered by the Geneva Conventions governing prisoners of war and should face consequences for their actions.


'They have committed crimes'


In an interview to US television network NBC News, Peskov said: "They are soldiers of fortune. They were involved in illegal activities on the territory of Ukraine. They were involved in firing at and shelling of our military personnel. They were endangering their lives." 


Ths was the first formal acknowledgment by the Kremlin that the two men, identified as Andy Huynh (27) of Hartselle, Alabama, and Alexander Drueke (39) of Tuscaloosa, Alabama, were being held and under investigation, according to Reuters.


The Russian media last week broadcast images of the two captured soldiers who had gone to Ukraine as volunteer fighters according to their families.


"...they should be held responsible for those crimes they have committed. Those crimes have to be investigated...The only thing that is clear is that they have committed crimes. They are not in the Ukrainian army. They are not subject to the Geneva convention," Peskov was quoted as saying in the Reuters report.


Asked about the specific crimes Drueke and Huynh had committed, the Kerimlin spokesperson said the offences were not yet known, Al Jazeera reported. Asked if the men could face the death penalty, he said it “depends on the investigation”, the report said.


Earlier, a court under the jurisdiction of separatists in Donetsk had sentenced two Britons and a Moroccan on grounds that they were mercenaries not subject to the Geneva Convention.