Social networks including Facebook, YouTube, and Odnoklassniki are inaccessible in Tajikistan following the release of a second video showing a former commander of Tajik special police forces who has defected to the Islamic State (IS) militant group.
There was no official explanation for the apparent ban from authorities in Dushanbe.
But Interior Ministry forces (OMON) commander Gulmurod Halimov's disappearance in April to join IS abroad has been a major embarrassment for Tajikistan, a poor and predominantly Muslim state that has struggled to discourage its young men from traveling to Syria and Iraq to fight for the radical Sunni group.
Tajik media reported that Internet users were unable to open the websites from midday June 18, hours after a video in which Halimov issues threats to "infidels," Russia, and the United States was published online.
In the video, Halimov and other armed men sitting in front of a black IS-style flag try to dispel rumors that he has gone to Syria on a mission to kill a high-profile Tajik militant, Nusrat Nazarov.
Nazarov, who goes by several other names, including Abu Kholidi Kulobi and Furqon Falastin, is a 39-year-old Tajik who has appeared in several IS videos claiming to be the leader of Tajik fighters in Raqqa.
Tajik media reported that Nazarov was killed recently in Syria.
In the video, Halimov does not mention Nazarov's death but says he "will remain a brother to Furqon forever."
Pointing to his gun, Halimov says he uses his weapon only to kill infidels: "If my own older brother or younger brother became an infidel, I would cut off his head. I would kill him if he fought against us."
In his first IS video, published on May 27, Halimov claimed he joined the brutal militant group to protest Tajik government restrictions on religious observance, such as its crackdown on Islamic clothing and limitations on mosque prayers. Wielding a gun, Halimov also threatened to bring holy war to Russia and the United States.
Popular social networks were blocked for several days in Tajikistan after the appearance of that first video.
Asomuddin Atoev, the chairman of Tajikistan's Association of Internet Service Providers, told RFE/RL's Tajik Service at the time that access to the sites was being blocked by some ISPs based on verbal instructions from the State Communications Service.
He said the order was based on coverage of the Halimov defection.
Halimov, 40, is wanted in Tajikistan for crimes that include high treason and illegal participation in military actions abroad.
The father of eight children, he had attended counterterrorism courses in Russia and the United States.
A lawyer by profession, Halimov joined the Tajik police force in the early 1990s and was appointed the head of OMON in 2012.