Anadolu Agency says the explosion occurred Monday in the mainly Kurdish city of Diyarbakir, close to its historic district of Sur, and caused a large crater.
The agency said the military immediately launched an operation, backed by air power, to catch the assailants.
The rebels of the Kurdistan Workers' Party, or PKK, have been fighting a separatist insurgency since 1984. The conflict has killed tens of thousands of people since then.
The group agreed to a cease-fire in 2013 but resumed fighting and violent attacks in 2015, after a fragile peace process with the government collapsed.