Ankara: Turkish police on Tuesday detained some 40 people, including a number of journalists, as part of a growing investigation into Kurdish activists' alleged ties to Kurdish rebels, the country's state-run television said.

The private Dogan news agency said a photographer working for the French news agency, Agence France Presse, and journalists for Kurdish media organizations were among the detained.

Dogan said the AFP photographer was arrested in Istanbul. The news agency would not immediately confirm the report.

The state-run TRT television said police conducted simultaneous raids in Istanbul and six other Turkish cities, detaining some 40 people.

They were to be questioned by anti-terrorism police in Istanbul, the station said.

The pro-Kurdish Firat news agency said at least 25 people were rounded up and that most of the detained are journalists working for Kurdish media organizations, including the Dicle news agency and the Birgun newspaper.

Hundreds of activists, including elected mayors, are already on trial accused of being part of a Kurdish umbrella group which prosecutors accuse of links to the autonomy-seeking Kurdistan Workers Party, or PKK.

The PKK has been fighting for Kurdish autonomy in Turkey since 1984. Tens of thousands of people have died in the conflict since then.

Tuesday's detentions are likely to further increase concerns over press freedoms in Turkey, a predominantly Muslim democracy that seeks membership in the European Union where dozens of journalists have been jailed, mostly on anti-terror charges.

They include journalists accused of aiding a hardline secularist network which prosecutors say plotted to bring down Prime Minister Recep Tayyip Erdogan's Islamic-rooted government.

The United States and the EU have criticized Turkey's press freedoms and there are calls for the country to revise anti-terrorism laws which have led to the arrests of the journalists as well as dozens of student protesters.

Turkish state media say the latest arrests are part of an investigation launched two years ago, during which time hundreds of Kurdish activists have been detained on charges of membership of the Union of Kurdistan Communities, a group prosecutors accuse of being an offshoot of the outlawed PKK. The activists deny the accusation.

In October, police also arrested a respected academician and a publisher as well as lawyers acting for the PKK's imprisoned leader Abdullah Ocalan in connection with their investigation into the group. No trial date has been set.