A Tajik leader, belonging to the country's Group 24 opposition movement, was killed in Istanbul late on Thursday.

Umarali Kuvatov was reportedly shot after a quarrel on a street in Fatih district, sources said.

The unidentified suspect fled the scene and the victim's body was transferred to a local morgue.

Officials said the case remains under investigation.

The Supreme Court of Tajikistan had labeled Group 24 an "extremist" group and banned its activities in October 2014. The court decision came after the opposition group made an online call for anti-government protests.

Tajik chief prosecutor's office claimed that Group 24's objective was to seize power in an unconstitutional manner, a charge the group said was politically motivated.