Warsaw/Moscow, Mar 26 (IANS): US President Joe Biden on Saturday called Russian President Vladimir Putin a "butcher" after meeting refugees in Warsaw, Poland, in an intense criticism of the Russian leader's actions in Ukraine that have seen millions of refugees flee to the neighbouring countries, CNN reported.

During his visit, Biden was asked by reporters what seeing the Ukrainian refugees at Stadion Narodowy made him think of as he deals with Putin every day.

Biden responded: "He's a butcher", CNN reported.

After initially looking to downplay a personal rivalry between himself and Putin, Biden has ramped up his rhetoric against Putin over the last 10 days.

Last week, Biden for the first time called Putin a "war criminal" and then later referred to him as a "murderous dictator, a pure thug who is waging an immoral war against the people of Ukraine".

He has also called the Russian invasion of Ukraine "inhumane", CNN reported.

Biden's new insults further narrow the window of opportunity for improving Russian-American relations. This was stated by the press secretary of Putin, Dmitry Peskov, RT reported.

"Of course, such personal insults narrow the window of opportunity for our bilateral relations under the current administration of the US. We must be aware of this," he was quoted as saying.

Peskov noted that the leader of the state must remain sober.