The U.S. confirms the death of an American presumed to be the second killed on the battlefield in Ukraine.

The U.S. State Department on Wednesday confirmed the death of a man believed to be the second American killed fighting in Ukraine.

The department identified the man, Stephen Zabielski, as a U.S. national who died in Ukraine but gave no further details. An obituary in the Recorder News in Montgomery County, N.Y., said Mr. Zabielski was a 52-year-old Florida resident and had died fighting in Ukraine in mid-May.

Mr. Zabielski’s death would mark the second American killed in combat in the war after Willy Joseph Cancel Jr., 22, a former Marine infantryman and a resident of Kentucky whose family said he was killed in late April fighting alongside the Ukrainian military.

The confirmation of Mr. Zabielski’s death also comes after a Kremlin spokesman said this week that two American fighters who had gone missing in Ukraine had been taken into custody. Alex Drueke, 39, and Andy Tai Ngoc Huynh, 27, were U.S. military veterans who had volunteered to fight in Ukraine.

A third American volunteer fighter may also be missing in action, the State Department said last week.

“We once again should take this opportunity to reiterate to Americans the inherent dangers of traveling to Ukraine,” said Ned Price, a State Department spokesman. “We understand certainly that there are Americans across this country — millions of Americans across this country — who feel motivated to support the righteous and the noble cause of the Ukrainian people.”

Mr. Zabielski’s family could not immediately be reached for comment.

Thousands of largely unregulated volunteer foreign fighters have flocked to Ukraine, only some of whom have been accepted into the Ukrainian Army’s International Legion.

Maham Javaid contributed reporting.