A bomb targeting a Turkish military convoy killed at least 28 people and wounded 61 in the country's capital Ankara during rush hour on Wednesday.
Ankara Governor Mehmet Kiliclar said the explosion was caused by a car bomb that detonated as the busses sat at a traffic light. Ruling Justice and Development Party (AK Party) spokesperson Ömer Celik said on Twitter that it was an "act of terrorism."
Turkish broadcaster NTV said the explosion happened near a bus carrying military personnel. Footage from CNN Turk showed what appeared to be a bus on fire, and a large plume of black smoke rising over the city.
A blast in Ankara last year killed more than 100 people; the Turkish government blamed the attack on the Islamic State (IS).
Turkey's military is involved in operations against IS in Syria, and is also embroiled in a bloody civil war in Turkey's Kurdish southeast. Kurdish separatists have in the past targeted Turkish security forces with bombs and ambushes.