The opposition accuses the authorities of setting up a cult of personality around Erdogan, who moved to the presidency in August after over a decade as prime minister.All of the latest arrests were related to nationwide demonstrations on Friday, when secular Turks boycotted schools and took to the streets to demand a secular education, the Dogan news agency reported.Onur Kilic, 25, the organiser of the demonstration in the western city of Izmir, was arrested on Friday for allegedly chanting "thief, murderer Erdogan", referring to corruption allegations against the president and his inner circle."I was told that I had been arrested for insulting the president but I haven't insulted anyone. I was just telling the truth" Kilic, who faces up to four years in prison, was quoted as saying by Dogan.Amnesty International on Monday called for "urgent action" to release Kilic and called on the government to end all prosecutions and detentions under a law that criminalises insulting the president.It said such prosecutions "violate the right to freedom of expression".Another protester, Kadir Yavas, was arrested on the same charge during a protest against Kilic's arrest, Dogan said.Arif Bugra Aydogan, a 20-year-old student, was arrested Monday after police raided and searched his home in the town of Gebze in Kocaeli province east of Istanbul.He was charged with insulting Erdogan after chanting slogans against him during the protest in Gebze.Another student, 24-year-old Safak Kurt, was also arrested on Monday after police found a video showing him shouting "Thief, murderer Erdogan!" during the protest in the southern province of Manisa.Meanwhile, a 17-year-old student, named only as H.U.C., was handed a seven-month suspended sentence in the southern city of Antalya on charges of "insulting a public official" in a 2014 anti-Erdogan speech, the Hurriyet daily reported.In power since 2003, Erdogan has been accused by critics of being increasingly authoritarian and intolerant of criticism.Protesters as well as journalists have in recent years found themselves facing criminal lawsuits or jail time after being accused of insulting of slandering Erdogan.In a case that attracted wide attention, teenage schoolboy Mehmet Emin Altunses will go on trial on March 6 on charges of insulting the president in a speech in the Anatolian city of Konya.