The Kremlin is upset about comments Bill O’Reilly made on Fox News, saying today it wants an apology over what it called “unacceptable” comments about Russian President Vladimir Putin.

O’Reilly reportedly described Putin as a “killer” in an interview with Donald Trump, as O’Reilly was challenging Trump about his apparent allegiance to Putin.

“O’Reilly did not say who he thought Putin had killed,” Reuters reports.

On a conference call, Kremlin spokesman Dmitry Peskov told reporters: “We consider such words from the Fox TV company to be unacceptable and insulting, and honestly speaking, we would prefer to get an apology from such a respected TV company.”

“Fox News and O’Reilly did not immediately respond to a Reuters request for comment,” Reuters notes.

The report adds: “Trump, when commenting on the allegations against Putin in the same interview, questioned how ‘innocent’ the United States itself was, saying it had made a lot of its own mistakes. That irritated some congressional Republicans who said there was no comparison between how Russian and U.S. politicians behaved.”

Trump was asked on Sunday to clarify those comments, Reuters notes, and told Westwood One Sports Radio: “Well, I don’t have to clarify it. The question was do you respect him — he’s a head of a major country.”