Eurovision Song Contest: Ukraine's Poroshenko hails win
Ukrainian President Petro Poroshenko has hailed his country's victory in this year's Eurovision Song Contest.
"An unbelievable performance!" he tweeted, thanking singer Jamala on behalf of the whole country.
However her song 1944 - about wartime deportation of Crimean Tatars - has angered many in Russia, which annexed Crimea from Ukraine in 2014.
Several Russian politicians and commentators blamed the result on hostility towards their country.
Jamala is the first Crimean Tatar to perform at the contest, which was held this year in the Swedish capital Stockholm.
The song 1944 caused controversy because of alleged political overtones. It references the year when Soviet dictator Joseph Stalin deported almost all of the Tatar ethnic group.
At a news conference, Jamala said the experiences of her great-grandmother had inspired song.
"This pain speaks to all the people who have experienced their own tragedies in the past, such as (the) Holocaust," she added.
Analysis: Tom Burridge, BBC News, Kiev
Like it or not, anything linked to Crimea in Ukraine today has, at the very least, political overtones because Russia's annexation of the peninsula remains an emotive topic and point of grievance for many Ukrainians.
That is especially true for Tatars like Jamala, who have left the peninsula and say they cannot return.
But the sombre nature of the song had appeared in some ways to be its Eurovision Achilles heel.
That's because the lyrics, in both English and Tatar, are hardly the type of catchy pop number that all too often comes out on top.
It makes Jamala's victory all the more remarkable.
"Yes!!!" President Poroshenko tweeted when the result was announced. "All of Ukraine gives you its heartfelt thanks, Jamala."
Ukraine's Vice-Prime Minister for European Integration, Ivanna Klympush-Tsyntsadze, denied that song was not a reference to the current conflict over Crimea.
"I don't think that there was any intention by Jamala to bring it to a political level," she told the BBC.
Political songs are not allowed at Eurovision but 1944 was permitted because it was based on historic fact.
However many people in Russia - which had been favourite to win the competition - have contended that the vote was political.
Russian MP Elena Drapeko blamed Russia's defeat on what she called an "information war" and "general demonisation" of her country.
Senator Frantz Klintsevitch told Russian media: "It is not Ukrainian singer Jamala and her song 1944 that won Eurovision 2016, it is politics that defeated art."
He called for a Russian boycott of next year's contest, in Ukraine.
There have been calls in Russia for a review of the outcome after a prankster - posing as an aide to Mr Poroshenko - told Russian TV that Jamala had admitted to him her song had a political subtext.
Pro-Kremlin media said the country had been robbed of victory by a new system of combining jury scores with public votes.
The official Rossiya 24 news channel says "TV viewers gave Russia victory", but alleges that the new voting rules "allowed the competition organisers to amend the results as they saw fit".
The juries from Russia and Ukraine did not award each other any points. However large numbers of the Russian public voted for the Ukrainian song, awarding it 10 points, while the Ukrainian public gave Russia's entry the maximum 12 points.