In this handout photo released by Turkish Presidency, Turkish President Recep Tayyip Erdogan, right, shakes hands with his Ukrainian counterpart Volodymyr Zelenskyy during their meeting at the Presidential palace in Ankara,

Russian negotiators at peace talks in Istanbul demanded Ukraine pull its troops out of all the Ukrainian regions claimed by Moscow before they would agree to a ceasefire, a senior Ukrainian official familiar with the talks told Reuters.