International rights groups have urged the UN to use the momentum of next month's conference to put an end to the persecution of critical voices in the Caspian country.

In a report released Tuesday, Human Rights Watch documented Azerbaijan's use of "politically motivated, bogus criminal charges to prosecute and imprison civic activists, journalists, and human rights defenders".

Any sign of dissent in Azerbaijan is usually met with a tough response from its government led by strongman President Ilham Aliyev, long accused by the West of persecuting political opponents and suffocating independent media.

"Azerbaijan is carrying out a vicious attack on government critics, independent groups, and media," HRW said in a statement.

It added that "the crackdown has intensified" ahead of COP29, which runs November 11 to 22.

"Azerbaijan should immediately and unconditionally free those unjustly imprisoned and end the crackdown," HRW said.

It listed journalists from media outlets critical of Aliyev and prominent anti-corruption advocate Gubad Ibadoglu who remains in custody despite poor health.

Azerbaijan's foreign ministry has rejected such accusations as "biased and unacceptable".

"Conditioning Azerbaijan's presidency of COP29 with inappropriate political motivation contradicts the very essence of the idea of cooperation addressing climate change that Azerbaijan has undertaken," it said in May.

Aliyev, 62, has ruled the energy-rich country with an iron fist since 2003, when he took over following the death of his father, Azerbaijan's Soviet-era Communist leader and former KGB general Heydar Aliyev.

The NGO Union for Freedom of Political Prisoners of Azerbaijan has published a list of 288 political prisoners, including opposition politicians, rights activists, and journalists.