The Kremlin has demanded an apology after a Fox News presenter described Vladimir Putin as a “killer” during an interview with Donald Trump.
Bill O’Reilly used the word while pressing the US President on whether he thought he would get along with the Russian leader.
“Putin’s a killer,” challenged O’Reilly.
“There are a lot of killers,” Mr Trump responded. “We’ve got a lot of killers. What, you think our country’s so innocent?”
Kremlin spokesman Dmitry Peskov said: “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.”
Mr Putin’s detractors have accused him of ordering the killings of opponents and critics.
In January 2016 a British judge ruled that the Russian president had “probably” authorised the murder of ex-KGB agent Alexander Litvinenko in London.
The Kremlin has repeatedly labelled such claims as false and politically motivated.
The Fox interview, aired before the Super Bowl, also saw President Trump questioned over whether he respected his Russian counterpart.
“I do respect him. Well, I respect a lot of people, but that doesn’t mean I’m going to get along with them,” said the President.
“Will I get along with him? I have no idea. It’s very possible I won’t,” he added.
Mr Trump’s remark comparing “killers” in both countries has also come under fire.
Fellow Republicans, including Senate majority leader Mitch McConnell, said there was no “equivalence” between the conduct of Russia and US.
“He (Putin) is a former KGB agent, a thug, not elected in a way that most people consider credible,” he said.
The two world leaders held their first phone call last week.
The Kremlin described the hour-long exchange as “positive”, while US officials described it as a “significant start to improving the relationship between the United States and Russia that is in need of repair”.
Mr Trump has signalled his wish for a better relationship with the country after things soured under Barack Obama.
The former president backed assessments that Russia hacked emails to influence the US election and that Mr Putin would have been aware.
Russian diplomats were expelled from the US after the controversy but Russia declined to do the same – a move Mr Trump praised as “very smart”.