KIEV, Ukraine — Several hundred people marched in Ukraine's capital Sunday to commemorate the brutal deportation 70 years ago of Crimea's entire population of Tatars, while about 20,000 members of the ethnic group rallied in the peninsula's main city.

The new Kremlin-backed leaders of Crimea had refused to allow the Tatars to hold their rally on a central square, so they gathered instead near a mosque on the outskirts. The Interfax Ukraine news agency said the crowd whistled in anger when two Russian military helicopters flew low over the gathering.

Moscow annexed Crimea in March. The Tatars, a Turkic ethnic group, now make up 12 percent of the population of Crimea, but they ruled the peninsula from the 15th century until the Russians conquered it in the 18th century.

In May 1944, shortly after Soviet troops drove German forces from Crimea, Josef Stalin accused the Tatars of collaborating with the enemy and ordered their deportation. About 250,000 Tatars were shipped in freight trains to Central Asia, where more than 40 percent died of hunger and disease.

Many Tatars later returned to Crimea in the years before and after the 1991 collapse of the Soviet Union, which led to Crimea becoming part of an independent Ukraine. The group now strongly supports the new Ukrainian government, which took power after the ouster of pro-Russia President Viktor Yanukoych earlier this year, and opposes Russia's annexation of the peninsula.

In Kiev, Tatar community leader Mustafa Dzhemilev, who was barred from Crimea after the Russian takeover, was among the marchers.

Another Tatar leader criticized authorities in Crimea, saying they interfered with the rally on Simferopol's outskirts. Refat Chubarov, chairman of the Tatar national assembly, condemned the "helicopters flying over a peaceful rally where people were praying for the souls of hundreds of those killed by the totalitarian regime" and complained that police had blocked the roads to prevent thousands of others from attending the ceremony, Interfax reported.

By banning the rally in central Simferopol, the Russians were "trampling on our memory, on an entire people," Chubarov said.