Turkish Prime Minister Recep Tayyip Erdogan has threatened to sue the Times of London for publishing an open letter by a group of celebrities, academics and others criticising his handling of anti-government protests.

Sean Penn, Susan Sarandon and Ben Kingsley were among those who signed the letter that accused Erdogan's government of "dictatorial rule" and of causing the deaths of five protesters who died after clashes with police.

If they truly believed in democracy, they couldn't have displayed such a lack of character to call the leader of a party that won 50 percent of the vote a dictator Recep Tayyip Erdogan,

Turkish prime minister

"The press wants to throw mud to see if it sticks. The Times is renting out its own pages for money," Erdogan told reporters on Friday in comments broadcast live by NTV channel.

"This is the Times' failing. We will pursue legal channels regarding the Times," he said.

Erdogan said the signatories of the letter, taken out as an full-page advertisement in the Times, had "rented out their thoughts" and did not genuinely support democracy.

"If they truly believed in democracy, they couldn't have displayed such a lack of character to call the leader of a party that won 50 percent of the vote a dictator," Erdogan said.

The letter also accused Erdogan of undermining the principles of a free press for jailing dozens of journalists in recent years.

The Times had no immediate comment on Erdogan's remarks.

Protesters demanded Erdogan resign as they staged the country's fiercest anti-government demonstrations in decades in Istanbul, Ankara and other major cities beginning in late May.

Many accused Erdogan of adopting an authoritarian tilt or greater religious conservatism after his AK Party won the last three general elections, increasing its share of the vote each time.

Erdogan has dismissed the protesters as "looters" and "terrorists" and accused foreign governments and media outlets of stoking the civil disturbances.