Turkish media say more arrests have been made and police heads dismissed in connection with a probe into official corruption. Prime Minister Tayyip Erdogan has called it a "dirty operation" aimed at undermining his rule.
The Turkish channels, NTV and CNN Turk, reported on Friday that another 14 heads of police units had been removed from their posts. The newspaper Hurriyet said eight people had been arrested, bringing the number of detainees since Tuesday to 50.
An exiled Muslim cleric, Fethullah Gulen, who was once a key electoral supporter of Erdogan's Justice and Development Party (AKP), has denied pressing via Turkey's secret services and its judiciary for the arrests.
The rift hit the headlines last month when Erdogan's government floated plans to close down private schools, most of them run by Gulen's Hizmet movement, exposing rifts in the premier's traditional power base.
The apparent feud follows mass protests in June, when mainly secularist demonstrators challenged what they described as Erdogan's increasingly authoritarian rule and moves to impose conservative Islamic values on society.
Arrests include ministers' sons
The 50 people arrested this week, mostly in Istanul and Ankara, include the sons of three cabinet ministers and well-known businessmen as well as five police chiefs.
Analyst Rusen Cakir said the Gulen movement had decided to "protect its interests." Since Erdogan's party first took office in 2002, Hizmet helped it to win three elections in a row.
Gulen has lived in exile in the United States since 1999 to escape charges of plotting against the secular state.
The crisis comes just days after Erdogan launched the AKP's campaign for Turkish municipal elections in March. A presidential election is due to be held in August, to be followed by parliamentary elections in 2015.
Erdogan is reported to be keen on becoming president if a constitutional amendment gives the post centralized powers.
Opposition calls for resignation
Turkey's opposition parties, including the Republican People's Party, have called on the government to resign and denounced the removal of Istanbul's chief of police, Huseyin Capkin (pictured above at front) earlier this week, as an attempt to shut down the probe.
The suspects include the sons of Interior Minister Muammer Guler, Economy Minister Zafer Caglayan and Environment Minister Erdogan Bayraktar.
Other detainees include the director of the state-owned Halkbank, Suleyman Aslan, a mayor belonging to Erdogan's ruling Justice and Development Party and a number of businessmen affiliated with the Turkish government.
The suspects are accused of accepting and facilitating bribes for some projects, getting construction permits for protected areas in exchange for money, gold smuggling and money laundering.
Gulen denies shadow role
On Wednesday, a lawyer for Gulen told the Dogan News Agency that the cleric denied being behind the probe.
"The honourable Fethullah Gulen doesn't have anything to do with and has no information about the investigations or the public officials leading them," Orhan Erdemli said.
Signs of deterioration in relations between Gulen and Erdogan emerged during the June protests.
The Turkish lira currency traded at an all time low compared to the US dollar early on Friday. In recent days, Istanbul's stock market has dipped more than 3 percent.
ipj/kms (AFP, dpa, Reuters)