* Police launch dawn raids, arrest at least 38 across Turkey
* Turkey has one of highest numbers of journalists in jail
* Arrests focus on alleged links with Kurdish militants
ISTANBUL, Dec 20 (Reuters) - Police detained at least 38 people, most of them journalists, in dawn raids across Turkey on Tuesday as part of an investigation into alleged links between Kurdish activists and armed separatist militants, security officials and media said.
Turkey already has some 70 reporters in jail, one of the highest numbers in the world, but says they are in prison for other crimes, not there for their work.
Jailing more journalists could fuel accusations that Prime Minister Tayyip Erdogan's government is intolerant of dissent and is trying to tame the media. But while the economy continues to grow rapidly, widespread public discontent is unlikely.
Police arrested 25 people in Istanbul, most of them journalists. Reuters witnesses saw Agence France-Presse photographer Mustafa Ozer being led away from his house by police. AFP in Turkey confirmed he had been detained.
More than 10 journalists from the pro-Kurdish Dicle news agency were also arrested, state-run Anatolian news agency said. A lawyer for Dicle said only police remained at the agency's Istanbul office, copying documents and computer hard drives. She said she did not yet know how many reporters had been taken into custody.
Hundreds of people, including elected mayors, are already on trial on charges of ties to the Kurdistan Workers Party (PKK) armed group as part of the same investigation which began two years ago.
In Diyarbakir, the main city in Turkey's restive mainly Kurdish southeast, police held at least six people, and carried out searches in 10 offices and houses belonging to Dicle staff, officials said. Simultaneous raids were also conducted in the capital Ankara, Izmir and other cities where arrests were also made.
Police also searched offices of several other news agencies across Turkey, seizing computers and documents, CNN Turk said.
Last month, more than 100 people were detained in similar raids which coincided with a surge in PKK attacks on Turkish security forces. These triggered military strikes against guerrilla bases in the mountains of neighbouring northern Iraq.
The investigation is focused on an organisation called the Union of Kurdistan Communities (KCK), which the PKK established in 2005 with the aim of creating its own Kurdish political system, according to a 2009 indictment.
Some 150 politicians and activists are already being tried in Diyarbakir, where a large courtroom has been specially built. Similar trials are being held in other cities across Turkey.
The arrests of yet more journalists could also spark further criticism in the European Union, which Turkey is aiming to join.
Due to the proliferation of such cases, Turkey has fallen to 138th out of 178 countries reviewed for the World Press Freedom Index by Reporters without Borders, a media freedom pressure group, from 101st in 2007.
More than 40,000 people have been killed in the conflict between the PKK and the state since the militants launched their armed insurgency in 1984. Turkey, the United States and European Union list the PKK as a terrorist organisation. (Writing by Ece Toksabay; Editing by Jon Hemming)