BAKU (Reuters) - Azerbaijan has voted in favor of extending the presidential term from five to seven years, election authorities said on Tuesday, a step that critics say will hand unprecedented powers to President Ilham Aliyev who has led the country since 2003.

Azerbaijan's President Ilham Aliyev casts his vote during a referendum on extending presidential terms in Baku, Azerbaijan, September 26, 2016. REUTERS/AZERTAC/Vugar Amrullayev/Pool

The state election commission said a vast majority of the 91.2 percent of voters who turned out in a referendum in the Caspian Sea oil-producer had backed the move.

“The referendum was conducted in a transparent manner,” Mazakhir Panakhov, commission head, said before reading out the result of Monday’s plebiscite.

Aliyev, 54, who succeeded his father as president, can seek re-election indefinitely after a maximum number of terms in office was scrapped via a similar referendum seven years ago.

The authorities say a longer presidential term will ensure continuity in decision-making, which they say is vital after a slump in world oil prices halted Azerbaijan’s long run of economic growth.

Apart from the high vote in favor of extending the presidential term there had also been strong support for another 28 amendments to the constitution, the election commission said. Turnout was 69.7 percent.

Opposition and rights activists criticized the amendments, which also give the president the right to declare an early presidential election at his convenience, as well as dissolve parliament.

Ahead of the vote, experts of the Council of Europe, a rights and monitoring body, said many of the proposed amendments being voted on would severely upset the balance of power by giving “unprecedented” powers to the president.

“A majority of Azeri voters expressed their confidence in Azerbaijan’s president,” said Ali Akhmedov, secretary of the ruling Yeni Azerbaijan party.

“The referendum results will have a positive effect on the implementation of economic reforms and will give an impetus to business development,” he said.

European observers from the Parliamentary Assembly of the Council of Europe (PACE) recognized the referendum results, but called on the Azeri authorities to improve the voting process.

“We think the referendum results are a step towards secure, stable and sustainable development of Azerbaijan and reflect the will of the Azerbaijani people,” said Aleksandar Nikoloski, who headed the PACE monitoring delegation.

“PACE hopes the Azerbaijani authorities will respect the opinion of the Venice Commission in all its aspects,” he added, referring to a Council of Europe advisory unit which had expressed reservations about the process.

European democracy watchdogs have said previous votes in the ex-Soviet Caucasus country of 9.7 million were marred by vote-rigging and unequal access to the media. The Baku government denies the charges.

Aliyev’s rule has long benefited from an economic boom fueled by oil pumped to Europe from a region where the West and Russia are vying for influence over huge energy reserves.

But a slump in global oil prices in the past two years has weakened the Azeri currency, the manat, and hurt the economy.