Crimea helicopters try to disrupt Tatar rallies
Military helicopters have flown low over a crowd of Tatars in Crimea, in an apparent attempt to disrupt rallies marking Stalin's mass deportations.
Speeches by local Tatar leaders were drowned out by the noise.
Mass gatherings were banned ahead of the 70th anniversary commemorations by the new leadership in Crimea, which was annexed by Russia in March.
Most Tatars opposed a disputed referendum, preferring to stay part of Ukraine.
Ukrainians are due to vote in presidential elections next Sunday but escalating tension between pro-Russia separatists and security forces in the eastern regions of Donetsk and Luhansk has affected preparations for the poll.
The central election commission has appealed to the Kiev authorities to ensure security because separatists have taken over a number of public buildings in the east,
UN Assistant Secretary General for Human Rights Ivan Simonovic told the BBC the crisis was approaching a "point of no return" in the east and had worrying echoes of the 1990s war in his native Croatia. In eastern Ukraine, 127 people had died since the violence began, he said.
He hoped the 25 May vote could take place in the east but said it would be "extremely difficult". The window for "inclusive dialogue" was closing, he added.
A crowd of several hundred joined a pro-separatist rally in central Donetsk on Sunday.
The separatists held referendums in the Donetsk and Luhansk regions a week ago and claimed to have won overwhelming popular backing.
Both the Ukrainian government in Kiev and Western countries regard the votes as illegitimate.
But a man appointed by the separatists as leader of their self-styled People's Republic of Donetsk said on Saturday that they would apply to join Russia.
Alexandr Borodai, 41, describes himself as a Russian citizen who had worked in recent months in Crimea as a political strategist.
In Crimea, two rallies were held, first in Bakchisaray and then on the outskirts of Simferopol, where at least 10,000 Tatars paid tribute to the 200,000 people deported by Stalin, mainly to Uzbekistan.
Almost half died and surviving families were only allowed to return in the late 1980s. They make up an estimated 12% of Crimea's population.
A decree banning major gatherings was issued on Friday by Crimea's authorities, who blamed the recent surge in violence in eastern and south-eastern Ukraine.
Tatar leader Refat Chubarov condemned the decision as an "inhuman act".
Because of the ban, Tatars walked to an ad-hoc ceremony guarded by Russian riot police, BBC correspondent Oleg Boldyrev reports.
As the two military helicopters flew over the crowd, people began chanting the name of their leader Mustafa Dzhemilev.
He took part in a rally in the Ukrainian capital, Kiev, where candles were placed on the ground in the shape of the Crimean peninsula.
Russian President Vladimir Putin met Tatar officials the same day, saying Moscow was ready to help them but refused to allow the Crimean Tatar population to become a "bargaining chip... in disputes between Russia and Ukraine".
The revolt in towns and cities in eastern and south-eastern Ukraine gained momentum after Russia's annexation of Crimea.
Moscow acted after Ukraine's elected pro-Russian President Viktor Yanukovych was ousted during unrest in the capital Kiev in February.
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