It is clear from the video, reported TV3, that Petrovs is in an Islamic country like Syria or Iran. He spoke Russian in a video published by Furat, a Daesh propaganda wire.
Jānis Luciņš, the new head of the Islamic Cultural Center, told TV3 that the country's Muslim community feels betrayed.
Petrovs was an outspoken public figure, lecturing about Islam across Latvia and often coming under flak for his quasi-radical views, which in the new video he repudiates as soft-spoken lies cooked for the media.
He was however a respected figure in religious circles as he had spent six years studying Islam in a Saudi Arabian university.
Laima Geikina, the head of the Theology Faculty at the University of Latvia, told Latvian Television that the radicalization of one Muslim shouldn't be viewed as representative of the whole Muslim community.
"Yes, [the Islamic Cultural Center] has conservative views, however I don't know whether they would radicalize the whole situation," she said.
This is not the first time Petrovs' activities have come under scrutiny by the Security Police.
Last year his views were examined as he suggested, after the Charlie Hebdo terrorist attacks where 12 died and 11 were wounded, that instead of being put to death the cartoonists apparently insulting Islam should still have undergone punishment, albeit of a less severe degree - like having their fingers broken.
If he has indeed joined an extremist group, Petrovs' is the third public case of Latvians who may have joined jihadist groups in the Middle East.
Petrovs was the first to announce that sociology student Māris Bergholds may have become a jihadist: "[..] he has in all likelihood become the first Latvian shahid," wrote Petrovs on the parislamu.lv website in 2012.