Soner Yalcin, who runs a news website fiercely critical of the government, was detained earlier this week in a case which triggered a diplomatic spat between Turkish officials and the new U.S. ambassador to Ankara.

Ambassador Francis Ricciardone, who said he did not know details of Yalcin's case, had remarked to reporters that it was hard to understand the detention of reporters in Turkey, given its avowed policy of supporting press freedom.

Turkish officials responded by warning the envoy against interfering in domestic affairs, and Foreign Minister Ahmet Davutoglu said it was not right for an ambassador to make judgments over an ongoing investigation.

Yalcin and two of his colleagues were charged with being members of a "terrorist group", "obtaining and publishing secret state security documents" and "inciting hatred", media reports said. Court officials were not available to comment.

Yalcin and his colleagues were questioned by prosecutors handling cases against the Ergenekon group, whose alleged members -- including lawyers, writers and politicians — are accused of conspiracies against the government.

Prime Minister Tayyip Erdogan attacked the main opposition leader for taking up the cause of Yalcin, his colleagues at the Odatv website, and the other Ergenekon defendants.

"Those from Odatv who are being tried now are not under investigation for their writing or thoughts, but for other actions," he told officials from his ruling AK Party.
 

Among the Ergenekon defendants, television station founder and writer Tuncay Ozkan told a court hearing on Friday he would run as a candidate in Turkey's June parliamentary election in the same district as Erdogan.

"I was brought here because I wanted to be in politics. My political right was obstructed. A non-existent group was created and we were brought here," said Ozkan, who played a prominent role in mass protests against the government in 2007.

"In the election I will be an MP candidate in Prime Minister Tayyip Erdogan's district," he was quoted as saying by state-run Anatolian news agency. He has been held on remand at Silivri jail, west of Istanbul, since September 2008.

He denied that his aim was to secure parliamentary immunity from prosecution.

Opinion polls show Erdogan's AK Party, which first came to power in 2002, is well ahead of its rivals in its campaign to win a third successive term in office.

On the Ergenekon issue, public opinion was behind the government after the first arrests back in 2007, as few Turks want a return to the coups that blighted the country in the late 20th century. Scepticism set in as the investigations broadened and many suspects have been held on remand for more than two years with no end in sight.

The trials reflect a lingering mistrust between the traditionally secular establishment and a ruling party that critics say retains Islamist leanings.

NATO member Turkey has pushed through a series of political reforms with the aim of securing EU membership, but rights groups remain critical of its record on freedom of expression.

The court cases revived debate about press freedom, as thousands of reporters have been investigated over their reports on the Ergenekon plots on the grounds that they violated the confidentiality of the cases.