The Kremlin said on Monday it wanted an apology from Fox News over what it said were "unacceptable" comments one of the channel's presenters made about President Vladimir Putin in an interview with US President Donald Trump. Fox News host Bill O'Reilly described Putin as "a killer" in the interview with Trump as he tried to press the US president to explain more fully why he respected his Russian counterpart. O'Reilly did not say who he thought Putin had killed. "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," Kremlin spokesman Dmitry Peskov told reporters on a conference call. Trump has long expressed a desire for improved relations with Moscow, but his latest comments about Putin and the US are leading some fellow Republicans to take a step back from the president — on this issue at least. Told by Fox News' Bill O'Reilly during an interview that the Russian leader is "a killer," Trump said the US has killers, too. "What do you think? Our country's so innocent?" Trump said during the taped interview broadcast during Sunday's Super Bowl pregame show. Trump says in the interview that he respects a lot of people, including Putin "but that doesn't mean I'm going to get along with him. He's a leader of his country. I say it's better to get along with Russia than not. And if Russia helps us in the fight against ISIS (Daesh), which is a major fight, and Islamic terrorism all over the world — that's a good thing," Trump said. "Will I get along with him? I have no idea." O'Reilly then said about Putin: "But he's a killer, though. Putin's a killer." Trump responded: "There are a lot of killers. We've got a lot of killers. What do you think? Our country's so innocent?" When O'Reilly says he doesn't know any US government leaders who are killers, Trump said "take a look at what we've done, too. We've made a lot of mistakes" and then he referenced the Iraq war. The Kremlin voiced anger over O'Reilly's characterization. O'Reilly also asked Trump to back up his claim that some 3 million to 5 million illegal votes were cast in the election. Trump didn't answer directly, but shifted to assert that immigrants in the US illegally and dead people are on the voter rolls. "It's really a bad situation, it's really bad," Trump said. There is no evidence of widespread voter fraud in the Nov. 8 election. Trump won the Electoral College vote but lost the popular vote by nearly 2.9 million votes to Clinton. Trump recently announced on Twitter that he would call for a "major investigation" into voter fraud. He said during the Fox News interview that he will set up a commission to be headed by Vice President Mike Pence and "we're going to look at it very, very carefully."