U.S. citizen Stephen Zabielski has died in Ukraine, the State Department confirmed to ABC News Tuesday morning.
Zabielski was a 52-year-old U.S. Army veteran. His death was first reported by Rolling Stone.
According to an obituary posted online by his family, Zabielski died on May 15 while fighting near a village called Dorozhniank.
"We can confirm the death of U.S. citizen Stephen Zabielski in Ukraine. We have been in touch with the family and have provided all possible consular assistance," a state department spokesperson told ABC News.
The State Department also said U.S. citizens should not travel to Ukraine because of the ongoing war and due to Russian government security officials singling out U.S. citizens in Ukraine.
Americans in Ukraine should depart immediately if safe to do so, the State Department said.
Willy Joseph Cancel, a 22-year-old former U.S. Marine, was killed in Ukraine in April while fighting aside Ukrainian forces. He was the first American to be reported killed in Ukraine.
Two U.S. citizens have been reportedly captured by Russian soldiers in the conflict zone in Donbas. Kremlin spokesperson Dmitry Peskov said he did not know their whereabouts, in a press briefing.
Peskov said they were mercenaries who made attempts on the lives of Russian service members. They are charged with mercenary practices, he said.
"The Geneva Convention absolutely does not apply to them. Their crimes must be investigated, and they must stand trial," Peskov said. As to whether the two Americans were facing the death penalty, Peskov said, "Yes, we do not rule out anything, because this is a decision to be made by a court, we never comment and, above all, have no right to intervene in court rulings."