By Daren Butler and Ayla Jean Yackley

ISTANBUL: Turkish police raided the offices of a conglomerate with close links to U.S.-based Muslim cleric Fethullah Gulen an ally-turned-foe of President Tayyip Erdogan company officials said on Tuesday.

Erdogan who wants to win back a majority for the ruling AK Party in a snap Nov. 1 election accuses Gulen of seeking to overthrow him by means of a "parallel structure" of supporters in the judiciary police the media and other institutions.

The state-run Anadolu Agency said 23 companies within the mining-to-media Koza Ipek group were being searched on suspicion of providing financial support for the "Gulenist Terrorist Group".

There was no immediate comment from the police. Interior ministry officials declined comment.

Erkan Akkus news editor at Kanalturk and Bugun TV which are part of Koza Ipek's media business said the holding company's headquarters and the chairman's home were being searched.

"The aim here is to silence the opposition media ahead of an election" Akkus told Reuters.

"It is wrong to see this as aimed just at our group. They are starting with us to test the waters and if it doesn't spark an outcry it could then spread to other media groups."

Koza Ipek Chairman Akin Ipek said in a written statement published by his media outlets that his group was not guilty of any wrongdoing and that the state had already thoroughly investigated "slanders" targeting his companies.

Shares in Koza Ipek companies including energy firm Ipek Dogal Enerji and miner Koza Madencilik fell 10 percent. Shares in other media firms not affiliated with Gulen also declined.

Anadolu Agency said the raids did not target the group's media companies. Bugun newspaper editor Erhan Basyurt said media firms appeared on the list of companies covered by the search warrant but that their premises had not yet been searched.

Opposition party leaders voiced concern about the police raids while Turkey's new European Union Minister Ali Haydar Konca warned against any raids targeting the media.

"I am worried that operations targeting the media will create great concern across the world about whether Turkey is a democratic country" the pro-Kurdish HDP's Konca part of the new power-sharing interim cabinet told a news conference.

INVESTOR CONCERNS

The operation came after a whistleblower account named "Fuat Avni" which has previously correctly forecast police raids said last week that Erdogan planned a crackdown on media critical of the government ahead of the November election.

Last week mainstream newspaper Milliyet dismissed five prominent journalists in a move described by the Turkish Journalists' Association as "unacceptable at a time when the country is tense with war and elections".

Late last year police detained dozens of people in raids on media outlets with ties to Gulen. Some of those journalists have been charged with terrorism-related crimes.

The operation against the Koza-Ipek group added to the worries of investors already rattled by political uncertainty and a surge in fighting between Turkish security forces and Kurdish militants.

"There is a risk that this sort of thing can intensify into the election and it really is underscoring the weak investment climate within Turkey" said Manik Narain EM strategist at UBS.

The cleric Gulen who has lived in self-imposed exile in Pennsylvania since 1999 has denied in the past any ambition to overthrow Erdogan. Gulen has also been charged for alleged "terrorist" activities.

The battle between Erdogan and Gulen became public in December 2013 when a corruption investigation targeting Erdogan's inner circle came to light. Related court cases were subsequently dismissed following a large-scale reorganization within the police and judiciary.

Erdogan blamed the cleric's supporters for the corruption allegations and purged thousands of police and members of the judiciary he deemed loyal to Gulen.

In his early years in power Erdogan drew on Gulen's influence in the judiciary to help tame the Turkish army which had toppled four governments since 1960 including the country's first Islamist-led cabinet through a series of coup plot trials.

Reuters