Khadija Ismayilova jailed for eight years over fraud charges she denounced as politically motivated.
Polls have closed in the first round of Azerbaijan’s presidential elections as it is widely expected to cement strongman President Ilham Aliyev’s grip on power in the country.
Some members of the opposition have staged a boycott over Sunday’s election, accusing the government of jailing amost all of its opponents.
International rights groups have also accused Azerbaijani authorities of limiting free speech.
The leading opposition party, Musavat, announced it was pulling out just four days before the vote.
“We have demanded that the authorities create democratic conditions and equal opportunities for all political forces” and postpone the vote, said its leader, Arif Hajili.
Hajili said only 24 of the 73 candidates nominated by the opposition party have been registered for the vote by the authorities.
Crackdown on opposition
The main trans-Atlantic security and rights group, the Organization for Security and Cooperation in Europe, has refused to monitor the vote after Azerbaijan demanded that it sharply cut the number of observers.
It marks the first time since Azerbaijan won independence after the 1991 Soviet collapse that the OSCE will not monitor its election.
“The Azerbaijani government’s crackdown on independent and critical voices has a particularly damaging effect ahead of the country’s November 1 parliamentary elections,” Isabel Santos of the OSCE Parliamentary Assembly said in a statement on Tuesday.
There are 767 candidates are vying for 125 seats in the country’s parliament, with around 5.2 million Azerbaijanis registered to vote.
International observers have not recognised any of the elections held in Azerbaijan since Aliyev came in power in 2003 as free and fair.
Amnesty International has protested what it described as “sustained and severe attack” on the freedom of expression in Azerbaijan in the run-up to the parliamentary election.
It said there are at least 20 prisoners of conscience in Azerbaijan who have been convicted on trumped-up charges ranging from fraud to treason.
Azerbaijani authorities have dismissed such criticism as unfounded.
Polling stations closed at 7:00 pm local time (1500 GMT), and the Central Election Commission was due to start releasing results later Sunday.