ISTANBUL » A year ago, journalist Nedim Sener was investigating a murky terrorist network that prosecutors maintain was plotting to overthrow Turkey’s Muslim-inspired government. Today, Sener stands accused of being part of that plot, jailed in what human rights groups call a political pogrom against the governing party’s critics.

Sener — who has spent nearly 20 years exposing government corruption — is among 13 defendants who appeared in state court this week at the imposing Palace of Justice here on a variety of charges related to abetting a terrorist organization. The other defendants include the editors of a staunchly secular website critical of the government and Ahmet Sik, a journalist who has written that an Islamic movement associated with Fethullah Gulen, a powerful and reclusive cleric living in Pennsylvania, has infiltrated Turkey’s security forces.

At a time when Washington and Europe are praising Turkey as the model of Muslim democracy for the Arab world, Turkish human rights advocates say the crackdown is part of an ominous trend. Most worrying, they say, are fresh signs that the government of Prime Minister Recep Tayyip Erdogan is repressing freedom of the press through a mixture of intimidation, arrests and financial machinations, including the sale in 2008 of a leading newspaper to a company linked to the prime minister’s son-in-law.

The arrests threaten to darken the image of Erdogan, who is lionized in the Middle East as a regional leader who can stand up to Israel and the West. Widely credited with taming Turkey’s military and forging a new brand of Islamic government that marries strong economic growth with democracy and religious tolerance, he has proved prickly and thin-skinned on more than one occasion. It is that sensitivity bordering on arrogance, human rights advocates say, that contributes to his animus against the media.

There are now 97 members of the media in jail in Turkey, including journalists, publishers and distributors, according to the Turkish Journalists’ Union, a figure that rights groups say exceeds the number detained in China. The government denies the figure and insists that with the exception of four cases, those arrested have all been charged with activities other than reporting.

Turkey’s justice minister, Sadullah Ergin, last month blamed civic groups for creating the false impression that there were too many journalists in jail in Turkey. He said a new plan to enhance freedom of expression this year would alter perceptions.

In court Wednesday, Sener, 45, looking gaunt and pale, blamed the police officials he had investigated for setting him up.

"It has been 11 months that I have not been given the chance to utter a single word to defend myself," he said, speaking to friends during a brief intermission. "I have been a victim in a revenge operation — nothing else."

The European Human Rights Court received nearly 9,000 complaints against Turkey for breaches of press freedom in 2011, compared with 6,500 in 2009. In March, Orhan Pamuk, a Turkish writer and Nobel laureate, was fined about $3,670 for his statement in a Swiss newspaper that "we have killed 30,000 Kurds and 1 million Armenians." Human rights advocates say they fear that with the Arab Spring lending new regional influence to Turkey, the United States and Europe are turning a blind eye to encroaching authoritarianism there.

"Turkey’s democracy may be a good benchmark when compared with Egypt, Libya or Syria," said Hakan Altinay, a senior fellow at the Brookings Institution. "But the whole region will suffer if Turkey is allowed to disregard the values of liberal democracy."

Among the most glaring breaches of press freedom, human rights advocates say, was the arrest of Sener, a German-born reporter who was working for the newspaper Milliyet at the time of his arrest. In 2010 he won the International Press Institute’s World Press Freedom Hero award for his reporting on the murder of Hrant Dink, a prominent Turkish-Armenian journalist who was assassinated in Istanbul in January 2007.

Sener said he believed that he was in jail because he dared to write a book criticizing the Turkish state’s negligence in failing to prevent Dink’s murder. His defense team says the prosecution’s case rests on spurious evidence, including a file bearing his name that an independent team of computer engineers concluded had been mysteriously installed by a virus on a computer belonging to OdaTV, an antigovernment website. He has been held for seven months without charges. If convicted, he faces up to 15 years in jail.

"Nedim Sener is being accused on the basis of rumors and fantasies," said his lawyer, Yucel Dosemeci. "He is being targeted to create a culture of fear."

In late December, Turkey drew fresh criticism after the police detained at least 38 people, many of them journalists, saying they had possible links to a Kurdish separatist group. But critics say dozens have been arrested whose only offense was to have expressed general support for the rights of Kurds, a long-oppressed minority here.

Over the past year, the government has been arresting prominent critics like Sener, as well as dozens of current and former military personnel, intellectuals and politicians who have been linked to what officials say was a plot to overthrow the government by an organization called Ergenekon.

Four years into the investigation, no one among the more than 500 suspects has been convicted, even though courts have heard more than 8,000 pages worth of indictments, many of them based on transcripts of surreptitiously recorded private telephone conversations.

Advocates for press freedom say that the government has also moved to mute opposition by using punitive fines and by intimidating the ownership of leading media companies.

In a celebrated case in 2009, the Dogan media group, a large conglomerate, was saddled with a $2.5 billion fine by the Tax Ministry for unpaid taxes. Dogan officials say privately that the real reason was that its publications had given prominent attention to a series of corruption scandals involving senior government officials.

The European Union has expressed concerns about the chilling effect of the fine, which was negotiated down to about $621 million, officials familiar with the case say, as part of a tax amnesty issued this year. Now, some journalists who work for the Dogan group say there is an unwritten rule not to criticize the governing party. Erdogan, who has previously called on his supporters to boycott the Dogan group, strongly denied any political motives behind the fine.

After Erdogan swept to power in 2002, human rights activists initially lauded him for expanding free speech. But after an unsuccessful attempt by the secular opposition to ban Erdogan’s party in 2008, critics say Erdogan embarked on a systematic campaign to silence his opponents.

Sener and Sik were defiant in March as police officers took them into custody at their homes before television cameras.

"Whoever touches it gets burned!" Sik shouted, referring to the Gulen movement, whose members, analysts say, have infiltrated the highest levels of the country’s police and judiciary.

In March, the unpublished manuscript of Sik’s book on the movement, "The Army of the Imam," was confiscated by police officers. But the police were unable to stop its publication on the Internet, where at least 20,000 users downloaded it.

While the Internet has become the main weapon against censorship, more than 15,000 websites have been blocked by the state, according to engelliweb.com, which tracks restricted pages. For more than two years until last fall, YouTube was banned on the grounds that some videos on the site were insulting to Mustafa Kemal Ataturk, the founder of modern Turkey.

The monitoring agency last summer called on websites to ban 138 words, including "animal," "erotic" and "zoo" in English and "fat," "blonde" and "skirt" in Turkish. It is a tribute to Turkey’s still vibrant media culture that the prohibition inspired an online competition to create the best short story out of the banned words.

© 2012 The New York Times Company