Turkey's president Recep Tayyip Erdogan has defended the crackdown on his opponents, including an arrest warrant for US-based arch-foe Fethullah Gulen, saying it is a "clean" legal process.

Erdogan's remarks came amid criticism from the European Union, which has said the "operation goes against the European values and standards Turkey aspires to be part of", a reference to Turkey's ongoing bid to join the bloc.

In a speech in Istanbul on Friday, Erdogan denied there had been any "lynching" of opponents and said the arrests were linked to a "coup plot" led by Gulen aimed at ousting him from power.

"I have been watching this process closely as president of this country. Everything is lawful and in line with procedure ... a really diligent and clean process is going on at the moment," Erdogan said in the televised speech.

"The police and judiciary are not repeating the mistakes of the past," he added.

Erdogan, who in August moved to the post of president after over a decade as prime minister, defended the detention of journalists as part of the probe, saying that some were using the profession as a "mask" for other activities.

He argued that the detention of journalists was nothing unusual, referring to the arrests in Britain over the phone-tapping scandal that rocked the tabloid press there.

Gulen arrest warrant

His comments came a day after an Istanbul court issued an arrest warrant for Gulen, who Erdogan accuses of running a "parallel state" from his exile in the US state of Pennsylvania.

A court on Friday also remanded in custody on terrorism charges the head of the pro-Gulen Samanyolu TV, Hidayet Karaca, and three police officers, although the editor-in-chief of the equally pro-Gulen Zaman newspaper Ekrem Dumanli was freed.

Seven other suspects were also released pending trial.

"God willing, no one will remember the era of the organisation of the assassins," Erdogan said, using one of his favoured terms for Gulen's group.

Dumanli - who is not allowed to leave Turkey and is still set to face trial - returned to his offices at the Zaman newspaper headquarters to a hero's welcome from hundreds of employees who shouted press freedom slogans, Samanyolu television pictures showed.

It remains doubtful that Washington will show any inclination to extradite Gulen, who has lived in the United States since 1999, to face trial in Turkey.

Gulen's movement, usually known as Hizmet (Service), has millions of followers and has built up a lucrative and influential international network of private cramming schools.

Supporters see the Gulen movement as a modern and forward-thinking Islamic-rooted group although some critics claim it has the makings of a cult.

Source: Agencies