Russians and Ukrainians sat face-to-face for under two hours on Friday in Istanbul for the first direct talks in over three years aimed at ending their war, with expectations low for breakthroughs.

Kyiv is seeking an "unconditional ceasefire" in Europe's deadliest conflict since the Second World War which has also destroyed large swathes of Ukraine and displaced millions of people.

Moscow says it wanted to address the "root causes" of the conflict and revive failed 2022 negotiations in which it made sweeping territorial and political demands of Ukraine.

Turkey's Foreign Minister Hakan Fidan sat at the head of a table in front of Turkish, Russian and Ukrainian flags at Istanbul's Dolmabahce Palace – with Russian and Ukrainian delegations facing each other, footage from the room showed.

The talks concluded after just over 90 minutes, a Turkish foreign ministry source said.

Speaking at a European summit in Albania, Ukrainian President Volodymyr Zelensky urged a "strong reaction" from the world if the talks fail, including new sanctions.

The two sides spent the 24 hours before the talks slinging insults at each other with Zelensky accusing Moscow of sending "empty heads" to the negotiating table.

Nevertheless, the fact the meeting was taking place at all was a sign of movement, with both sides having come under steady pressure from Washington to open talks.

Russian President Vladimir Putin declined to travel to Turkey for the talks, which he had proposed, sending a second-level delegation instead.

Zelensky said Friday Putin was "afraid" of meeting, and criticised Russia for not taking the talks "seriously".

Both Moscow and Washington have also talked up the need for a meeting between Putin and US President Donald Trump on the conflict. (AFP)