Russia and Ukraine started a major prisoner exchange on Monday after days of wrangling cast doubt over the only concrete result of peace talks last week in Turkey.

A prisoner exchange is under way between Russia and Ukraine, governments in Moscow and Kyiv have confirmed. Ukraine's President Volodymyr Zelensky said the exchange would unfold "in several stages" over the coming days,

Russia struck Ukraine with a thunderous aerial bombardment overnight, further dampening hopes that the warring sides could reach a peace deal anytime soon.

Russian and Ukrainian delegates met in Istanbul on Monday for their second set of direct peace talks, a day after Kyiv launched a shock drone attack on Russia’s nuclear-capable bombers, in an operation that President Volodymyr Zelensky said was a year and a half in the making.

It restated Moscow's demands that Ukraine become a neutral country - ruling out membership of NATO - and that it protect the rights of Russian speakers, make Russian an official language and enact a legal ban on glorification of Nazism. Ukraine rejects the Nazi charge as absurd and denies discriminating against Russian speakers.