My bets or on PKK (and Iran backing them)
PKK was trying to change the place this new war fought on or at least halt it, they tried nearly everything, tactical nuclear, killing civilians, chemical/biological weapons, TSK burning it's own soldiers etc. etc.
This is actually a pretty good way to inflict fear and terror, leading into population thinking recent operations not being successful, moreover some people won't even believe X group this kind of things thus claiming AKP (P.S, I am not an AKP supporter, people who know me in real life or Twitter would know this) or deep state did this, further improving the damage dealt by PKK
I wish God's mercy to all the citizens who lost their lives and condolences to their relatives. The Turkish people are not a country that can be intimidated by terrorist attacks. If there are still those who have not learned, we will teach them.
Starting from the Metina-Gara-Zap-Avashin-Basyan regions, the Northern Iraqi countryside has become the grave of the PKK. This mountainous geography between Iraq and Turkiye was the vital territory of the PKK terrorist organization, and the upper hand has largely, and soon completely, passing to the Turkish Armed Forces. This means an end to the flow of militants and trafficking, as well as the complete opening of the road to Qandil. Despite pkk's best efforts to attract world attention, Turkish commando is now on the PKK's throat.
The fact that the TSK has begun to destroy this 40-year-old problem at its very source seriously disturbs two countries besides the PKK. Some of you may remember that a few months ago the PKK organized an attack on civilians in the ZAHO region and a PSYOP against the TSK was launched immediately afterwards. At the time, Iranian-backed militia groups showed solidarity with the PKK, promising on their telegram accounts that they would carry out terrorist attacks on Turkish territory. These threats were so intense that they were even reported in the US, European and Israeli media. If you search the archives a bit, you can find a lot of documents.
In short, this terrorist attack is still very hot and it is difficult to say anything until the details are cleared up. However, it is important to keep in mind that there may be people who want to overshadow and obfuscate the structure that carried out this terrorist act, and if the PKK is the terrorist organization in question, there may be insidious structures, co-operations inside it. Lastly, If it is as I think it is, Turkiye is about to break the balls of that ox.