ANKARA - Turkey has ordered the arrest of the Muslim cleric Fethullah Gulen and seven others over the 2016 assassination of the Russian envoy to Turkey, the Haberturk newspaper said on Monday, a day before Russian President Vladimir Putin visits the country.Andrei Karlov was shot dead by an off-duty policeman while speaking at an Ankara exhibit opening in December 2016. The gunman shouted "Allahu Akbar" and "Don't forget Aleppo!" as he opened fire, apparently referring to Russia's involvement in neighboring Syria. He was shot dead by police at the scene.Putin arrives on a two-day visit on Tuesday and will meet President Tayyip Erdogan and Iranian President Hassan Rouhani. Their three countries are the guarantors of the Astana peace talks that has set up "de-escalation" zones across war-torn Syria.Erdogan said Gulen's movement was behind the assassination, a charge the cleric has denied. Erdogan also blames the preacher's network for an attempted military coup in July 2016.Gulen, who has lived in self-imposed exile in the United States since 1999, has denied the charge and condemned the coup.