Several leading Kurdish politicians have joined a weeks-long hunger strike demanding an end to the isolation of Abdullah Ocalan, the jailed leader of the Kurdistan Workers Party (PKK) who is currently serving a life sentence in prison.
The mayor of Diyarbakir, a predominantly Kurdish city in southeastern Turkey, said in a statement on Sunday that he had stopped eating. Five Kurdish members of parliament also said they are on hunger strike.
The politicians join some 700 Kurdish inmates, a mix of militants and political activists with links to the PKK, who have spent more than eight weeks on hunger strike.
Ocalan has been kept in solitary confinement on an island near Istanbul since 1999. His lawyers have not been allowed access to the island for 15 months.
The hunger strikers are also demanding that they be allowed to speak Kurdish in court. The language has been subject to widespread restrictions for decades. It was banned in schools until earlier this year, when Turkish Prime Minister Recep Tayyip Erdogan announced plans to allow it as an elective subject.
The Turkish government insists that none of the prisoners are in critical condition yet. They are consuming water and sugary drinks, which allows them to prolong their strike.
But several members of the Republican People's Party, the main opposition party, told Turkish media that prisoners they met during a tour of detention facilities were showing symptoms of starvation.
Local media reports said the government is negotiating with members of the Peace and Democracy Party, the main Kurdish party, to end the hunger strike.
Erdogan's government has boosted Kurdish cultural and language rights since taking power, but activists want greater concessions, including steps towards autonomy for southeastern Turkey.
There are about 15 million Kurds in Turkey, one-fifth of the population.
The PKK, which wants an independent Kurdish state, has staged some of its bloodiest attacks in more than a decade this year as tensions grow between Turkey and its neighbour, Syria, which Ankara has accused of arming the group.
More than 40,000 people have been killed in the conflict between the Turkish state and the PKK, which is designated a terrorist organisation by Turkey, the United States, and the European Union.