TURKISH POLICE arrested 39 people suspected of links to an alleged coup plot yesterday, as fears grew that what some dub the most important criminal investigation in Turkey’s history is being undermined by political pressure and spiralling social tensions.

Five active army officers and 17 police, including special forces officers, were among the men detained in a dawn sweep across the country, broadcasters said. Their arrest pushes the number of people detained since investigations started in June 2007 to more than 200.

The trial of 86 people, including retired senior officers, accused of planning a string of high-level assassinations to destabilise the country and force military intervention, began last October.

Ergenekon, as Turks call the group, has divided the country since the start. Some think it is a plot sponsored by the Islamic-rooted AK Party government to discredit rivals. Others see it as a key test in EU candidate Turkey’s march towards full democracy.

Tensions sky-rocketed earlier this month following the arrest of 40 men, including two retired top generals, a former head of Turkey’s Higher Education Board, and a retired state prosecutor. All four men played a key role in toppling an Islamist government, the predecessor of the current ruling party, in 1997.

“This is a regime change, like in the Khomeini and Hitler eras,” the head of Turkey’s secular chief opposition party Deniz Baykal said on January 10th. The same day, Turkey’s staunchly secular army chief called an unscheduled meeting with prime minister Tayyip Erdogan. Two days later, the four men were released.

The meeting sparked widespread speculation that the military was stamping down on investigations. In fact, the January 10th sweep appears to have given investigators a second wind. “They really hit the nail on the head,” says Cuneyt Ulsever, a columnist for Hurriyet, Turkey’s biggest daily.

He was referring to the arrest of former police special forces chief Ibrahim Sahin, and the discovery in his house of sketch maps that led to an arms cache on the outskirts of Ankara. But Sahin’s importance is much greater than the weapons he may or may not have buried in 2004, analysts say.

Appointed police chief of a small central Anatolian town in 1980, he procured passports for known ultra-nationalist killers, one of whom was involved in the assassination attempt on Pope John Paul II a year later.

He reappeared alongside the same men in the 1990s, at the head of a new police special forces unit established to use extraordinary measures in the ongoing war against Kurdish separatists. When the extent to which the state had dabbled in organised crime became clear in 1996, Sahin was one of very few state officials sentenced to jail.

“Follow Ibrahim Sahin’s footsteps, and you have a chance to uncover the sources of the illegality at the heart of the Turkish state right back to the 1970s,” says Can Dundar, a well-known broadcaster who has been following state-Mafia relations for over a decade. “With a well-run investigation, Turkey has the key now to clean up decades of dirt.”

The problem is that the investigation is not being well handled. The 2,450-page indictment against the 86 suspects in the dock is a vague mishmash of different elements. Analysts compare media coverage of Ergenekon to the organised campaign that preceded the toppling of the Islamist government in 1997.

“Back then, secular newspapers were full of leaked intelligence reports about fundamentalism,” remembers Rusen Cakir, a leading journalist. “Now, pro-government newspapers are full of leaked reports about putschists. This is not just an investigation. It is a war, with psychological operations run by the police, and the media acting as police, prosecutor and judge.” Media irresponsibility claimed its first victim this Saturday when a retired senior military intelligence officer committed suicide at his Ankara home following reports in the press linking him to a series of unsolved murders during the 1990s. The entire military high command turned out for his funeral.

Yet this display of solidarity doesn’t necessarily mean army chiefs are taking sides over the investigation. In fact, the army began cleansing itself of putschist elements long before Ergenekon kicked off. Informed of two coup plans in 2003 and 2004, the then chief of staff Hilmi Ozkok blocked both, and began sidelining the leaders.

The current army chief has a reputation for being a much more hawkish secularist, but he has not blocked investigations. Two retired top generals arrested last year were taken by police from their flats in a military compound, something that would have been unthinkable just five years ago. With the army the backbone of Turkey’s strategic relationship with the West and the US, it efforts to cleanse itself are understandable. All the officers arrested in connection with Ergenekon seek an end to Turkey’s Nato membership and EU bid and closer relations with Russia, China and even Iran.

Hilmi Ozkok has made it clear he is willing to give evidence in court regarding the coup attempts he foiled in 2003 and 2004. Why, analysts ask, hasn’t the prosecutor called him, given that the two suspected ring leaders have been in custody for nearly a year.

For Murat Yetkin, Ankara bureau chief of the liberal secularist daily Radikal, the answer is simple. “Rather than trying to uncover the truth, [the prosecutor] is trying to fit facts to his preconceived ideas,” he says.

A former AKP minister, President Abdullah Gul met leading politicians, judges and army officers on Wednesday to calm frayed nerves. “Many people’s names are being used by newspapers and TV stations in a very irresponsible way,” he said before the meeting.

“The press should act very cautiously . . . Not doing so may lead to a polarisation of the country, which would damage Turkey greatly.” Can Dundar fears Mr Gul’s intervention comes too late. He thinks Ergenekon has turned into a trial of force between the government and secularists in the army and judiciary.