Prosecutor says US-based cleric wanted to cause a 'provocation' between Turkey and Russia with the murder of Andrei Karlov in 2016
Turkey has charged 28 people in relation to the 2016 assassination of the Russian ambassador to Ankara, naming the US-based cleric Fethullah Gulen as the prime suspect in the case.
Andrei Karlov was shot dead by Mevlut Mert Altintas, an off-duty policeman, while inaugurating a photo exhibition in the Turkish capital in December 2016.
The gunman shouted "Allahu Akbar" and "Don't forget Aleppo!" as he opened fire, apparently referring to Russia's involvement in Syria.
Altintas, 22, was killed shortly after the murder by members of Turkey's special forces.
President Tayyip Erdogan has said Gulen and his Hizmet (Service) movement were behind the killing and has also blamed the cleric's network for an attempted military coup in July 2016.
Gulen denies both accusations.
The prosecutor said on Friday that Gulen's movement was a spy and intelligence organisation that wanted to cause a "provocation" between Turkey and Russia with the murder.
At the time of the killing, ties between the two countries had already been strained, after Turkey downed a Russian war plane over Syria a year earlier.
'Seeking to create terror'
The 28 suspects are charged with "violating the constitutional order" and "being a member of a terror organisation," as well as "premeditated murder with the intention of causing terror" and "seeking to create terror or panic".
The prosecutor sought varying terms, including aggravated life sentences, which have replaced the death penalty in Turkey and carry harsher conditions than normal life imprisonment convictions.
In April this year, a Turkish court issued arrest warrants for eight people, including Gulen, over the murder, the AFP news agency reported.
Among those sought by Ankara, and also named in Friday's indictment, was Serif Ali Tekalan, who headed a university linked to Gulen in Istanbul and now heads the Texas-based North American University.
Although Turkey has issued multiple arrest warrants for Gulen, who has lived in self-imposed exile in the US since the 1990s, Washington's failure to extradite the Pennsylvania resident has been a source of tension between the NATO allies.