SIMFEROPOL, Ukraine (AFP) - Russian flags flooded Lenin Square in the centre of Crimea's capital Simferopol on Sunday as thousands rallied in support of Moscow's takeover of the peninsula - vastly overwhelming a smaller pro-Ukraine demonstration nearby.

The rival rallies in Simferopol were peaceful, in contrast to the Crimean port city of Sevastopol, where about 100 pro-Russians with clubs and whips attacked some 20 people who were guarding a pro-Ukraine rally.

Some 10,000 people joined the pro-Russia rally in Simferopol, chanting "Russia! Russia!" as a navy band played patriotic Russian songs and dancers twirled on stage.

"We will overcome all adversity, all obstacles and we will restore historic justice," the newly installed pro-Russian Prime Minister of Crimea, Mr Sergei Aksyonov, told the crowd. "Together with Russia we will build our future!" he cried, prompting shouts of "Hurrah! Hurrah!" from the crowd.

Standing amidst signs reading "Crimea is not in Ukraine" and "With Russia, Peace in Crimea," 60-year-old Ms Olga said restoring Crimea to Russian rule would undo a historical injustice.

"We don't want to be with those Ukrainian fascists any more," said Ms Olga, who declined to give her surname.

A few kilometres away, a much smaller crowd of about 1,000 gathered for a more sombre demonstration in support of Crimea remaining within Ukraine.

Standing under a bronze bust of Mr Taras Shevchenko - the Ukrainian poet and national hero whose birth 200 years earlier was marked on Sunday - the demonstrators read poetry and sang the national anthem, many with their hands on their hearts.

"We are here to honour the great Shevchenko and Ukraine," said Mr Svyatoslav Regushevsky, a 46-year-old who brought his 21/2-year-old son, wearing a ski jacket with the Ukrainian flag colours, to the unity rally.

"They cannot seize Crimea, (it's an) illegal occupation," he said, as around him unity supporters waved yellow-and-blue balloons marked: "We are for peace in Ukraine".

The atmosphere was peaceful, with several dozen police keeping watch on the edges of the crowd.

A convoy of about 30 cars tooting their horns and waving Russian flags drove by the rally, prompting shouts of "Shame! Shame!" from participants.

Asked why so many more people were at the pro-Russia rally, 32-year-old Mr Anton Vlasenko said they were afraid to stand up to Moscow.

"They are scared of the Russian soldiers, they think they have no choice," he said.

He said the referendum planned for March 16 on making Crimea part of Russia - announced after pro-Moscow lawmakers seized control and Russian forces flooded into the region - was a farce.

"The Kalashnikov is the symbol of Russian democracy," Mr Vlasenko said.

Attempts to hold a similar pro-unity demonstration in Sevastopol were met with violence, with the pro-Russian activists attacking some 20 people who were guarding a 200-strong rally in an outer district of the city.

The attackers destroyed a car and blocked the vehicles of the security men guarding the crowd, at least five of whom were detained by police.

It was unclear whether anybody was seriously injured in the clashes at the rally, which also saw protesters waving the Ukrainian flag and singing the national anthem.