It is weird to hear US President Joe Biden, the man who called for bombing Yugoslavia and killing people, raising accusations against Russian President Vladimir Putin, Kremlin spokesperson Dmitry Peskov said Saturday.

Biden's personal insults against Putin narrow the window of opportunity for improving relations between Moscow and Washington, Peskov added.

"Still, a state leader should keep their temper," he told TASS, commenting on a certain remark that came from Biden.

He stressed that such personal insults from the current administration in Washington undermine the prospect of bettering Russian-US bilateral relations. "It is necessary to be aware of this."

President Biden had called his Russian counterpart a "butcher" after meeting with Ukrainian refugees in Poland.

The Democrat had also cast doubt on the Russian statements assuring that the aim of its war was helping the people of the eastern Donbass region after they were subject to bombardment and discrimination from the Kiev regime for nearly a decade.

"I am not sure [the Russians] have [changed their strategy]," Biden told the press after meeting refugees in Warsaw.

Russia had launched a special military operation in Ukraine over NATO's eastward expansion, the Ukrainian shelling of Donbass, and the killing of the people of the Donetsk People's Republic and Lugansk People's Republic, in addition to Moscow wanting to "denazify" and demilitarize Ukraine.