Istanbul map

Umarali Kuvvatov had settled in Turkey, who had refused to extradite him to Tajikistan. (Google Maps)

An outspoken critic of veteran Tajik leader Imomali Rakhmon has been shot dead by an unknown assailant on a street in Istanbul, Turkish media reported on Friday.

Umarali Kuvvatov, who had been living in exile in Turkey and was head of the "Group 24" opposition movement, was killed with a single shot to the head at around 10:30 pm on Thursday evening in the Fatih district of the city, Dogan news agency said. The attacker then fled the scene.

Istanbul police declined to comment on the case.

Turkey's anti-terrorism police unit and murder squad are handling the investigation into the killing of Kuvvatov, who had been eating dinner at a house in the area before he was shot, Dogan said.

The 47-year-old businessman was already dead when medics arrived at the scene and police searched the area for evidence, it said.

Kuvvatov had accused President Rakhmon, a 62-year-old former head of a Soviet state farm who has governed the impoverished central Asian republic since 1992, of rampant corruption and nepotism.

A spokesman for the Tajik prosecutor-general's office said it had information about the killing but gave no details. He said Tajik prosecutors had not yet been in contact with their Turkish colleagues about the shooting.

Turkish paper raises spectre of poisoning

Turkey's Sabah newspaper said Kuvvatov and his family had fallen ill after eating dinner with a fellow Tajik, who has since been detained by police. It said Kuvvatov had left his house to take his wife and children to hospital.

The paper quoted people close to Kuvvatov as saying he and his family may have been poisoned before he was shot. It said the assailant was believed to be Tajik and had said a few words before opening fire.

Kuvvatov's "Group 24" movement was declared an "extremist organization" and banned by Tajikistan's Supreme Court last October. Tajik law enforcers wanted him for a number of crimes, including extremism, economic crimes and hostage-taking. Turkey had declined to extradite him.

Kuvvatov had worked for a company trading oil products that was headed by one of Rakhmon's relatives. He founded his movement in 2012 after emigrating to Russia.

When Tajikistan asked Moscow to extradite him, he moved to the United Arab Emirates where he was detained at the request of Tajik police. He then settled in Turkey.