A Turkish police bomb disposal expert walks at the site of a blast in central Ankara. (Reuters)

Initial reports, from the Associated Press, claim that the explosion was triggered by either a bomb planted in a car, or a canister thrown onto vehicles from a nearby building. Turkey’s interior minister says three people died in the explosion.

On Twitter, a message being passed around claimed credit for the blast, saying, “We, as the Revolutionary Monarchist Front - Girayists, claim full responsibility for the bomb blast in republican capital Ankara. Please RT.” It is unclear what the group is, or who they represent.

Turkey, an important U.S. ally, has been attacked by Islamic militants in the past, as well as by Kurdish rebels fighting for autonomy in southeastern Turkey.

Here are some scenes from the blast site: