Smoke rises after an explosion at a riot police building in the southeastern province of Diyarbakir in Turkey on April 11, 2017. (Xinhua)

ANKARA, April 12 (Xinhua) -- The Kurdistan Workers' Party (PKK) on Wednesday claimed responsibility for a bomb attack in southeastern Turkey, local media reported.

A statement issued on a PKK website said more than 2.5 tons of explosives had been planted in a tunnel under the targeted police building in the central Baglar district of Diyarbakir province.

The explosion on Tuesday occurred during the repair of an armored vehicle in the provincial security directorate compound, which killed three people and injured 12 others.

Turkish Interior Minister Suleyman Soylu confirmed early Wednesday that the incident was "a terror attack" after initially calling it an accident, daily Hurriyet reported.

Investigations have revealed that PKK militants dug the tunnel in a short time and staged the attack by placing explosives underground.

A 30-meter-long tunnel was dug from the basement of an apartment adjacent to the repair shop of the compound, the Diyarbakir governor's office said in a statement.

According to the office, five suspects had been detained as a part of the investigation into the attack.