The first reports appeared already in mid-July. First it was Kurdish news Agency Firat, who reported about the corresponding decision of Turkish authorities on July 18th and about the transportation of 200 jihadists to Azerbaijan. Later there were some other Kurdish sources (e.g. Hawar News Agency) claiming the same.
On Sep 22nd, few days prior to war, Lindsey Snell, a prominent journalist writing on the region of Middle East, published a photo supposedly with Hamza group militants, in a plane arriving to Baku via Ankara.All those reports were initially not taken seriously, given the prejudice towards Turkey
However, starting from Sep 28th several international news agencies, including The Guardian, Reuters, BBC, The Independent, AFP, Le Monde, Der Spiegel, Deutsche Welle, Wall Street Journal, The Washington Post, Foreign Policy and others reported on the participation of Syrian militants on the Azerbaijani side. Most if not all of the abovementioned journalists stated to have personally talked to militants recruited in Syria by Turkey for fighting on Azerbaijani side, some links can be found in the comments below.
The first video, showing Syrian jihadists in Azerbaijan, appeared on Sep 27th, the first day of war. On the video there are some uniformed people on trucks, crying “Allahu akbar”. The video was geolocated in the city of Horadiz. Initially the geolocation was not totally convincing, but later evidences proved it.
On Sep 30th a video from an SNA military base was released, showing mercenaries being trained in the uniforms of Azerbaijani Border Guards. The base was geolocated in northern Syria, right on the border with Turkey , the uniforms belonging to SNA and Azerbaijani Border Guard is also obvious, also here.
Next clear video-evidence appeared on Oct 3rd, showing some Arabic speaking people in the uniforms of Azerbaijan’s State Border Service. The video was undoubtedly shot in Azerbaijani Border Service’s border control unit’s base in Horadiz (video 1 , video 2 and video 3).
On Oct 10th a video with Arabic speaking fighters, wearing Azerbaijani Border Guards uniform, was released. The exact geolocation is not known (as far as I know) but it seems to be somewhere close to southern borders of Nagorno-Karabakh.
There was another bold evidence from Oct 10th with a jihadist militant broadcasting from the battlefield and claiming “they will kill all unbeliever pigs with the help of Allah”. I will not post a link to this video for the ethical issues, but it was clearly geolocated in Marjan.
Unnecessary to say, that this list is not complete. Dozens of other videos and photos have also been published, which I did not list here since some further verification is needed concerning the geolocation or affiliation of the militants. I will however update this list in due time. All abovementioned videos are of course saved and archived.
As of Oct 15th the participation of Syrian militants was confirmed by Russian MFA, French President, Iranian President, a Pentagon official, etc., Syrian Observatory for Human Rights confirmed the transfer of at least 1650 fighters to Azerbaijan.
Azerbaijan and Turkey continue to officially reject it.
Research source: Facebook of Aram Khachatryan