Two Americans captured in Ukraine while fighting with Kyiv's military were "endangering" Russian soldiers and should be "held accountable for those crimes," Kremlin spokesman Dmitry Peskov said Monday in an interview with NBC News.

The interview marks the first time the Kremlin has commented on the cases of Alexander Drueke and Andy Huynh, both U.S. military veterans, according to NBC.

"They are not [in the] Ukrainian army, so they are not subject to the Geneva Conventions," the Kremlin spokesman said.

Last week, a Russian state TV channel aired videos on social media of Drueke and Huynh. 

The circumstances under which the two men were being held were not fully clear, nor who specifically was holding them. Peskov would only say they were being held by "authorities."

As to whether they could face the death penalty, Peskov said: "It depends on the investigation."

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