Turkish authorities on Saturday detained a key suspect in a bombing that killed seven people and wounded 23 in the biggest attack of its kind in months in the strife-hit southeast, security sources said.

The outlawed Kurdistan Workers Party (PKK) claimed responsibility for Thursday's bombing in the mainly Kurdish city of Diyarbakir, one day before Prime Minister Ahmet Davutoglu visited the city and outlined plans to confiscate and rebuild a historic neighbourhood ruined in clashes since July.

Sources said police apprehended a man they believe parked the bomb-laden car and detonated it when a minibus carrying police officers passed it on a busy street. On Friday, authorities arrested nine people in connection with the bombing.

Separately, militants late on Friday used a car bomb to strike a military outpost near the town of Kiziltepe by the Syrian frontier. One civilian was killed and 13 people wounded, including three children and two soldiers.

A police officer from a combat unit was killed on Saturday in Yuksekova near the Iraqi border, where security forces began operations and imposed a round-the-clock curfew on March 13.

The predominately Kurdish southeastern region of Turkey has seen the worst violence in two decades after the PKK abandoned a two-year ceasefire in July and resumed its armed campaign for autonomy. The government says more than 5,000 militants and almost 400 soldiers and police officers have been killed.

Opposition parties estimate that between 500 and 1,000 civilians have also been killed in the fighting largely focused in densely populated urban centres.