Voters in the oil-rich Caspian Sea nation of Azerbaijan are casting ballots in a parliamentary election expected to secure the ruling party's dominance.

International rights groups have accused authorities of limiting free speech, and the main trans-Atlantic security and rights group, the Organization for Security and Cooperation in Europe, has refused to monitor Sunday's vote after Azerbaijani authorities demanded that it cut the number of observers.

Azerbaijani President Ilham Aliyev's government long has faced criticism in the West for showing little tolerance for dissent and holding elections that fall below democratic standards.

Opinion surveys have indicated a strong lead for the ruling Yeni Azerbaijan party, the results reflecting a rise of incomes in the nation of 9 million under Aliyev's watch, thanks mainly to the country's oil wealth.