As a government it is never a good idea to kill your own soldiers because sooner or later the truth starts leaking out.
An excerpt from, "Ankara Bombing Fails To Achive Strategic Changes" by b, Moon of Alabama, February 18, 2016:
The bombing in Ankara yesterday killed 27 mostly military people. It was a big car bomb and a suicide attack.The Turkish government claims that the person who did this was one Saleh Nejar and also claims that he is connected to the Syrian Kurdish group YPG.An excerpt from, "YPG Statement on Recent Attack in Ankara – Turkey" Kurdistan Tribune, February 18, 2016:
There is no way to verify this. But the YPG has so fare never used any car bombs or done any suicide attacks. It never touched any target in Turkey. It officially denied to have taken any part in it.
The Turkish group PKK has done vehicle bomb attacks and a few suicide attacks but not in Ankara or any other major west-Turkish city. Its attacks are usually operational, not strategic like this one.
In the last Turkish version of its magazine the Islamic State had called for attacks in Turkey and on Turkish soldiers. It is the entity that has most to win through such an attack that would predictably be blamed on the Kurds. It is the most plausible culprit.
“As is known to our people and the public opinion, Rojava revolution has entered its 4th year. As YPG forces, we are protecting our people in Rojava region from the very first day on. Under challenging conditions, we are protecting our people from barbaric gangs such as ISIS and Al-Nusra. Countless states and media outlets have repeatedly reported about the support Turkey has been providing to these terrorist groups. Apart from the terrorist groups attacking us, we as YPG have engaged in no military activity against the neighboring states or other forces. Despite all its provocations and attacks on Rojava border, we have acted with historic responsibility and never retailated Turkey. During the past 4 years, Rojava is the safest area of Turkey-Syria border, and there has been no military action conducted by our side during this period. This truth is best known to the Turkish military and AKP government. They are deliberately distorting the truths and holding us responsible for the explosion in Ankara.
We would like to reiterate our message to the peoples of Turkey and the world; We have no links to this incident. It is not specific to this case alone, as we have never been involved in an attack against Turkey.