DUSHANBE -- Relatives of the main suspect in the killing of Tajik opposition tycoon Umarali Quvatov in Turkey say he is innocent.
Tajik citizen Sulaimon Qayumov, 30, and five co-defendants went on trial in Istanbul last month.
Prosecutors want Qayumov sentenced to life in prison if he is convicted. They say he organized the killing of Quvatov, who once had close ties to Tajik President Emomali Rahmon but became an opponent and was wanted by Dushanbe on fraud charges that he said were politically motivated.
Quvatov was shot in the head on an Istanbul street on March 5, shortly after he left Qayumov's home when he suddenly felt ill during a visit.
Qayumov's brother, Rahmon Qayumov, told RFE/RL on August 2 that his brother had nothing to do with the slaying.
He contended that the suspect had simply invited Quvatov and his family to his apartment in Istanbul to commemorate Qayumov's father, who had died in Tajikistan on that day.
Quvatov, his wife, and their two sons felt sick after eating food offered by Qayumov and rushed out for fresh air and an ambulance.
Quvatov's wife, Kumriniso Hafizova, later told RFE/RL that when they were outside, an unidentified man approached Quvatov from behind and fired a single shot to his head before fleeing.
Quvatov died at the scene. His wife and sons were provided with medical assistance and released from the hospital after they felt better.
According to Hafizova, an autopsy concluded that Quvatov was poisoned before being shot.
Qayumov and five other Tajik nationals were arrested later and charged with involvement in the killing.
Quvatov, 47, left Tajikistan in 2012 and stayed in Russia and the United Arab Emirates before moving to Turkey.
Tajikistan formally requested his extradition in January.
Quvatov had worked for a company trading oil products that was headed by a relative of Rahmon.
After leaving Tajikistan he accused Rahmon, who has governed Tajikistan since 1992, of corruption and nepotism.
Cracking Down On Opposition
Group 24, which Quvatov founded from abroad, has come under increasing pressure in the past year as Rahmon has sought to consolidate his grip on the poor former Soviet republic.
Tajikistan's Supreme Court banned Group 24 in October 2014, after the government labelled it an extremist group.
Also in October, the Tajik authorities blocked hundreds of websites after Group 24 used social media to call for a big antigovernment protest in Dushanbe.
Since then, several Tajik activists have been sentenced to lengthy prison terms for alleged association with Quvatov's group.
Quvatov was killed four days after parliamentary elections that were marred by suspected violations, criticized by international observers, and dismissed as a "farce" by the Communist Party leader.
Rahmon's party won the most votes, according to the official results, and no opposition party won any seats.