MINNEAPOLIS — The son of a 98-year-old Minnesota man sought by Polish authorities in connection with a Nazi massacre reiterated Saturday that his father is innocent and asked that evidence against him be released.

A court in Poland issued an arrest warrant for Michael Karkoc earlier this week, opening the way for Poland to seek his extradition from the United States on war crimes charges. The Associated Press had previously identified Karkoc as an ex-commander in an SS-led unit that burned Polish villages and killed civilians in World War II.

Karkoc’s son, Andriy Karkoc, called on U.S. Sens. Amy Klobuchar and Al Franken to intervene in his father’s case “on legal and humanitarian grounds” and to investigate the source of the evidence against him, which Andriy Karkoc says was fabricated by Russian intelligence.

“The Associated Press and the KGB may provide something they say is proof,” he said. “But what they cannot provide is something that is true. My father was, is, and remains an innocent man.”

AP spokeswoman Lauren Easton said the AP stands by its stories, calling them well-documented and thoroughly reported.

A spokesman for Klobuchar says the senator believes the matter should be addressed in the criminal justice system, not the U.S. Senate. Franken was traveling from northern Minnesota to Washington on Saturday and was unavailable for comment.

Earlier this week, prosecutors from the Institute of National Remembrance in Poland said evidence shows that American citizen Michael K. was a commander of a unit in the SS-led Ukrainian Self Defense Legion that raided eastern Poland’s village of Chlaniow in July 1944, killing 44 people, including women and children.