On Friday, a suicide bomber struck the U.S. embassy in Ankara, Turkey, killing himself and a Turkish guard, according to provincial governor Alaattin Yuksel. The bomber reportedly detonated his charge as he entered the embassy's security checkpoint, limiting the blast to the facility's outer ring.

Suspicion immediately fell on the Kurdistan Workers Party, or PKK, a separatist group in Turkey that the U.S. has designated a terrorist organization. However, Turkey is no stranger to terrorist attacks, and it's more than possible that another group was responsible. In 2003, a truck bomber allegedly affiliated with al Qaeda killed 58 people in an attack on the British consulate in Istanbul. In 2008, another al-Qaeda-linked attack killed three policemen outside the U.S. consulate in Istanbul.

Furthermore, Turish Prime Minister Recep Erdogan has been a fierce critic of Syrian President Bashar al-Assad, who is in the midst of a brutal civil war. 

The PKK's co-founder, Sakine Cansiz, was recently shot and killed in Paris, in what many believe to be a political assassination designed to disrupt fledgling negotiations between Erdogan's government and another PKK official, Abdullah Ocalan. The attack on the U.S. embassy, by implicating the PKK, could feasibly be a similar attempt at disrupting those talks.