Residents of Crimea, the Black Sea peninsula that Russia annexed from Ukraine in March, are voting for their regional parliament in elections expected to be dominated by Russian President Vladimir Putin's backers.

A spokesman for Ukraine's national security council, Volodymyr Polyovyi, told reporters Sunday that Ukraine considers the election illegal and that those responsible for holding them could be charged with seizing state power, which carries a prison sentence of up to 10 years.

Crimean news reports said pre-election opinion polls indicate the United Russia party, Putin's main supporter in the Russian national parliament, was likely to get the largest share of the 100 seats in the regional parliament. The Just Russia and Liberal Democrat parties, which support Putin, also were likely to win seats, as was the Communist Party.