Ukraine's foreign ministry condemned "sham elections" being staged by Russia in occupied Ukrainian territories on Friday, saying they were "worthless" and would have no legal standing.
Russia is holding regional elections, including in four Ukrainian regions that it does not fully control - Donetsk, Luhansk, Zaporizhzhia and Kherson.
The ministry said in a statement that the elections taking place on Ukrainian territory "grossly violate the sovereignty and territorial integrity of Ukraine" as well as international law.
"Russia's sham elections in the temporarily occupied territories are null and void. They will not have any legal consequences and will not lead to a change in the status of the Ukrainian territories captured by the Russian army," it said.
Kyiv called on its international partners to denounce the votes and not to recognise the results.
US Secretary of State Antony Blinken on Thursday also described the voting in Russian-occupied areas of Ukraine as "sham elections" and said they were "illegitimate".
The Russian embassy in the US responded by saying on Friday that Washington was meddling in Russia's internal affairs.
The US and Iran failed to reach an agreement to end their war despite marathon talks that concluded on Sunday in the Pakistani capital Islamabad, jeopardising a fragile ceasefire.
Russia and Ukraine accused each other on Sunday of breaching the 32-hour ceasefire in their four-year war, reporting more than a thousand drone and shelling attacks just hours after the truce began on Saturday to mark Orthodox Easter.
At least 30 people were killed on Saturday in a stampede at the Laferriere Citadel in the northern countryside of Haiti, authorities said, warning that the death toll could rise.
A cyclone battered New Zealand's North Island on Sunday, cutting power to thousands of residents and forcing hundreds to evacuate, as officials warned conditions would worsen through the day.
Negotiations between the United States and Iran appeared to have concluded for now, Iran's government has announced early on Sunday, after a series of talks in Pakistan to end the six-week war between Washington and Tehran.