"We can confirm the recent deaths of two U.S. citizens in the Donbas region of Ukraine," a State Department spokesperson said. "We are in touch with the families and providing all possible consular assistance."
They added: "Out of respect to the families during this difficult time, we have nothing further."
One of the Americans killed was Luke Lucyszyn, his mother, Kathy Lucyszyn, confirmed to ABC News.
A former U.S. soldier who served with the two Americans told "Good Morning America" they faced overwhelming Russian firepower.
"There was artillery basically 24-7," the soldier said. "They could shoot at us but we couldn't even see them."
This is a developing story. Please check back for updates.