Azerbaijan's President Ilham Aliyev has won a third five-year term in office, with nearly 85 percent of the vote in an election that international monitors have termed "seriously flawed".
Opponents of Aliyev, including the main opposition candidate Jamal Hasanly, said on Thursday that they aimed to challenge the official result in the Constitutional Court, alleging violations including ballot stuffing and multiple voting.
"This election was neither free nor fair," Hasanly said.
International monitors from the Organisation for Security and Cooperation in Europe (OSCE) said the vote was marred by a "restrictive media environment" and allegations of intimidation of candidates and voters.
"The limitations placed on the fundamental freedoms of assembly, association, and expression, the lack of a level playing field, the allegations of intimidation, all came in the lead up to an election day that our observers found to be seriously flawed," OSCE official Tana de Zulueta said.
Monitors reported clear indications of ballot-stuffing at 37 polling stations, and said the counting was assessed negatively at 58 per cent of stations observed.
An OSCE news conference degenerated into chaos as journalists from pro-government media drowned out the observers and shouted "The OSCE is biased".
The US State Department said that Washington agreed with the OSCE that the election "fell short of international standards".
In a statement, it urged the government to respect freedom of peaceful assembly, association and speech and to prevent violence in the post-electoral period.
Standing before a national flag on state television, the president, who succeeded his father a decade ago as leader of the oil-producing former Soviet republic, lauded the poll as a "triumph for democracy", pledging over the next five years to crack down on rampant corruption that critics claim his rule has fostered.
Allegations of corruption
Aliyev, 51, has overseen an economic boom that has largely raised living standards in the Caspian Sea nation, which pumps oil and gas to Europe, bypassing Russia. He has allowed Washington to use it as a transit point for sending troops to Afghanistan.
But he has faced criticism at home and abroad over his treatment of opponents. Media are tightly controlled, protests quashed, and one rights group said a pre-election crackdown had doubled the number of political prisoners.
A gaping divide between the rich and poor and allegations of corruption, which Azerbaijanis say pervades many aspects of life, has led to an increase in unrest, and the opposition said that it was planning a rally on Saturday.
But few expect sustained protests over a vote whose results many saw as a foregone conclusion because of Aliyev's tight grip over the South Caucasus nation of nine million people.
Rights groups say Azerbaijan's strategic location between Russia and Iran, its oil reserves, Europe-bound energy pipelines and support role for US operations in Afghanistan have cushioned it from Western criticism.
Aliyev has dismissed accusations of human rights abuses and says citizens enjoy full democratic freedoms.
A huge issue for his new term will be the festering conflict with Yerevan over the Armenian-controlled region of Nagorny Karabakh, which Aliyev's administration had threatened to win back by force.
Despite years of negotiations since Armenian-backed separatists seized the region in a 1990s war that killed 30,000 people, the two sides have still not signed a final peace deal.