Lviv Mayor Andriy Sadovyi, who attended the service, said on Facebook that Swift had fought for Ukraine's International Legion, and earned an award during his service.

"Sincere condolences to the family and eternal memory to the defender," Sadovyi wrote.

According to a statement by the U.S. Navy, Swift deserted from the U.S. military in 2019, and was killed while fighting in Ukraine on Jan. 18.

The service, held at a Catholic church in Lviv's historic centre, was attended by several dozen mourners, including Swift's brother, Thomas.

(Reporting by Roman Baluk; writing by Max Hunder; editing by Jonathan Oatis)