President Recep Tayyip Erdogan's government is cracking down more aggressively on dissent and political opponents ahead of Turkish elections with censorship and prison sentences, Human Rights Watch says.
Presidential and parliamentary elections are set for no later than mid-June but Erdogan has said they could come earlier.
Polls show he and his Islamist-rooted AK Party could lose after 20 years in power.
In its annual World Report, the rights watchdog said authorities were using online censorship and disinformation laws to muzzle independent media, the opposition and dissenting voices.
"The government has carried out highly abusive manoeuvres against the political opposition, blanket bans on public protest and the jailing and conviction of human rights defenders and perceived critics by courts operating under political orders," Human Rights Watch Europe and Central Asia director Hugh Williamson said in the report.
Turkey's Directorate of Communications did not immediately respond to a request to comment.
Last month, a court sentenced Istanbul Mayor Ekrem Imamoglu, a potential Erdogan challenger from the main opposition Republican People's Party (CHP), to two years and seven months in prison and handed him a politics ban for insulting public officials in 2019 - a verdict he has appealed.
Erdogan said in response Turks have no right to ignore legal rulings and courts would correct any mistakes in the appeal process.
This month, the top court froze the bank accounts of the pro-Kurdish Peoples' Democratic Party (HDP), parliament's third-biggest party, while it hears a case on shutting it down over alleged ties to militants.
The party denies the claims.
In October, Turkey adopted a law proposed by the AK Party that would jail journalists and social media users for up to three years for spreading "disinformation", sparking deep concerns about free speech.
Critics have said there is no clear definition of "false or misleading information", leaving the law open to abuse by courts that are not independent.
The government denies their claims that courts cracked down on open dissent and silenced opponents in recent years.
The government says the new law aims to regulate online publications, protect the country and combat disinformation.