Istanbul prosecutors Friday began charging some of the prime minister's closest allies in a huge graft scandal which he has responded to with a spectacular purge of the police.

Recep Tayyip Erdogan has said he was battling "a state within a state" and described the corruption probe, which comes ahead of crucial March polls, as a smear operation.

A sweeping corruption investigation implicating some of Turkish Prime Minister Recep Tayyip Erdogan's closest allies is threatening to weaken his grip on power ahead of key elections next year.

At least 51 people including the sons of three ministers and several top business leaders were detained in a series of dawn raids on Tuesday, in the biggest investigation into official corruption since Erdogan took office in 2002.

The Istanbul police chief has been dismissed after dozens of people including the sons of cabinet ministers were detained in a sweeping graft probe, media reports said Thursday.

Huseyin Capkin, who had been at his post since June 2009, is the latest of 30 senior police officers to be sacked in Istanbul and Ankara for "abusing their power".

Turkish Prime Minister Recep Tayyip Erdogan charged Wednesday that the detention of dozens of people in a high-profile graft probe was an "ugly" operation against his government.

Five police chiefs have been sacked in the wake of the dawn raids on Tuesday which led to the arrest of the sons of three ministers and several top business leaders, sending shockwaves through Turkey's political establishment.

Five Turkish police chiefs have been dismissed after dozens of people including sons of cabinet ministers were detained in a high-profile probe into bribery and fraud, media reports said Wednesday.

The police raids on Tuesday and the subsequent sackings have highlighted deep rifts in Prime Minister Recep Tayyip Erdogan's support base ahead of key elections in Turkey next year.

A Turkish man who called the 1915 Armenian genocide "an international lie" had a right to express his views and should not have been convicted by a Swiss court, the European Court of Human Rights ruled Tuesday.

The 2007 conviction of Dogu Perincek, an Ankara-based chairman of the Turkish Workers' Party, on charges of racial discrimination was "unjustified", the judges said.

Turkish photographer Bunyamin Aygun has disappeared in neighboring Syria while covering the civil war there, his newspaper said on Tuesday.

"We haven't received any news from our journalist, who was on a reporting mission, for more than two weeks," an official from the Milliyet newspaper told Agence France Presse.

Turkey's defense minister on Tuesday denied reports that his country was delivering weapons of war to Syrian rebels, but acknowledged that "hunting rifles" had been exported to Syria.

"No war weapons have been exported to Syria in 2013," Ismet Yilmaz said in parliament, according to media reports.

Four pro-Kurdish lawmakers went on hunger strike in the Turkish parliament on Tuesday to denounce a court ruling against the release of jailed MPs with suspected links to Kurdish rebels.

The MPs launched their action after branding Monday's court decision affecting five lawmakers who have been held since 2010 as "discriminatory".

Turkish police detained more than 20 people including the sons of three cabinet ministers and several high-profile businessmen on Tuesday in a probe into alleged bribery and corruption, local media reported.

Istanbul governor Huseyin Avni Mutlu confirmed the raids but declined to comment on the details.