Tajik opposition politician and businessman Umarali Quvatov was buried on March 9 in Istanbul, where media reports said three Tajik men were arrested on suspicion of involvement in his killing last week.
Quvatov's relatives told RFE/RL that the burial at the Kilyos cemetery followed the janaza, the Islamic funeral prayer ceremony, conducted at the Fatih Mosque in Istanbul's Fatih district.
Mourners unfurled a banner that said: "The killer of Tajik opposition leader, martyr Umarali Quvatov, is dictator Emomali Rahmon," the Tajik president.
Quvatov's wife, Kumriniso Hafizova, told RFE/RL on March 8 that her husband had been shot in the head on a street in Istanbul by an unidentified attacker last week.
Hafizova confirmed earlier reports saying that on March 5, she, Quvatov, and their two sons had been invited for dinner at the house of Sulaimon Qayumov, a 30-year-old Tajik citizen who has been residing in Istanbul for several months.
Hafizova said that she, Quvatov, and their sons felt sick after consuming food offered by Qayumov and rushed out for fresh air. An ambulance eventually arrived at around 10:30 p.m.
When they were outside, Hafizova said, an unidentified man approached Quvatov from behind and fired a single shot to his head before fleeing.
Quvatov died at the scene.
Hafizova and her two sons were hospitalized and diagnosed with poisoning. She was later released to take care of three other children who remain at home, while her two sons continue to receive treatment in the clinic.
According to Hafizova, an autopsy concluded that Quvatov was poisoned before being shot. It is not clear what substance was used to poison Quvatov and his family members.
Amnesty International issued a statement on March 6 calling on Turkish authorities to "lead an impartial, effective, and prompt investigation into" Quvatov's "unlawful killing, reveal the full truth, and bring the perpetrators to justice."
Turkish media reports said on March 9 that three Tajik men, including Qayumov, had been arrested on suspicion of involvement in Quvatov's killing.
A tycoon who once had close ties with President Emomali Rahmon but became an opponent, Quvatov was wanted by Dushanbe on fraud charges that he said were politically motivated.
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.
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, after the government labeled it an extremist group.
Tajik authorities had blocked hundreds of websites after Group 24 used social media to call for an antigovernment protest in Dushanbe on October 10.
Tajik Interior Minister Ramazon Rahimzoda said in January that several Group 24 members have been detained in Russia and were expected to be extradited to Tajikistan, and that three more associates of Quvatov were arrested in Tajikistan.
At least two Tajik activists have been sentenced to lengthy prison terms since October for their 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.
With reporting by Hurriyet and Haberturk.com