Citizens of the Caucasus country are voting on changes to Azerbaijan's Constitution, which would give more powers to President Ilham Aliyev.
Opposition and rights groups say the proposed changes are undemocratic.
If passed, the amendments would extend the president's term in office from five to seven years. A new first vice president would be installed and the president would get the power to call snap elections and easily dissolve the parliament, AP reported. Opposition groups staged protests ahead of the polls, denouncing them as President Aliyev's plan to tighten his family's grip on the country. The former Soviet republic has vast oil resources.
The Council of Europe also criticized the draft modifications, saying their implementation "would severely upset the balance of power by giving unprecedented powers to the president".
According to Amnesty International, the amendments would lead to violations of individual freedom.
"The referendum has been accompanied by arrests and intimidation ... Those who have attempted to criticize and campaign against these proposals have faced assaults and harassment by the authorities," Amnesty said in a statement. President Ilham Aliyev, 54, has led his country since his father, Heydar Aliyev's death in 2003. He won a landslide victory in polls in 2013, with OSCE observers pointing out several problems with the vote.
The next elections are in 2018 and President Aliyev is expected to contest yet again after a 2009 referendum scrapped the limit of two terms for a candidate.
