Ilham Aliyev, President of the Republic of Azerbaijan, pictured on the opening day of the 48th annual meeting of the World Economic Forum, WEF, in Davos, Switzerland. File picture: Gian Ehrenzeller/Keystone via AP

Baku, Azerbaijan - The president of Azerbaijan has called a snap presidential election.

Ilham Aliyev, who has ruled the oil-rich Caspian Sea nation since 2003, had been expected to seek re-election in November, but his office announced on Monday that an early election would be held in April. Aliyev's office did not immediately explain the move.

Azerbaijan's constitution was amended at a referendum in 2016, extending the presidential term from five to seven years. Aliyev's critics saw the referendum as effectively cementing a dynastic rule. The 56-year old Aliyev succeeded his father, who died in 2003.