Turkey's Recep Tayyip Erdogan on Friday waded into the war of words between the US and Russian presidents, chastising Joe Biden for calling Vladimir Putin a "killer."

"Mr Biden's comment about Putin does not suit a head of state," the Turkish president told reporters after Friday prayers in Istanbul, lauding Putin for giving a "smart" and "classy response".

In an interview with ABC News, Biden was asked if he thought Putin was "a killer".

"I do," Biden replied, immediately sparking the biggest crisis between Russia and the United States in years.

Putin on Thursday mocked the US leader, saying a Russian phrase that translates roughly as "it takes one to know one", and wishing Biden, 78, good health.

"I'm saying this without irony, not as a joke," Putin, 68, said.

Erdogan's comments reflect a new spell of tensions that have entered Turkey's relations with Washington since Biden replaced Donald Trump in the White House in January.

Erdogan is still waiting for a phone call from Biden, whose administration has highlighted Turkey's deteriorating record on human rights.

Turkish-US relations are also hampered by Ankara's purchase of advanced S-400 air defence systems from Moscow, which Washington says threaten NATO defences.

Biden is also remembered in Ankara for calling Erdogan an "autocrat" in an interview in late 2019.

Despite their differences on Syria, Erdogan has called Putin a "friend and a strategic partner."