April 12 (UPI) -- An explosion in a repair shop at a police compound in Turkey was the result of a "terror attack" and not an accident, the country's interior minister said Wednesday.
Süleyman Soylu said on private broadcaster Habertürk that explosives were planted Tuesday in a tunnel dug beneath the police headquarters in the the mainly Kurdish city of Diyarbakır in southeastern Turkey.
"The explosion occurred while an assistant technician was repairing an armored vehicle there," Soylu said. "As of last night, it became clear that it is a terror attack.
He said the surroundings are inspected about once a month.
"They [assailants] staged the attack through a tunnel dug from the outside," Soylu said. "We scan our police buildings almost every month to prevent such a threat. In this case, they dug such a tunnel in a very short time. They staged the attack by placing explosives underground."
On Tuesday, Soylu said the blast occurred from a vehicle under repair and appeared to be an accident and there were no signs of any "outside intervention."
Two civilians and a police officer, Burhan Mercan, were killed, and 12 were injured in the blast that was heard throughout the province. The repair shop collapsed in the explosion, and other nearby buildings and vehicles were damaged.
The governor's office said the tunnel was 100 feet long and its entrance was an adjacent building. It said 2,200 pounds of explosives were planted.
The Kurdistan Workers' Party, a militant group, accepted responsibility for the attack after the interior minister's comments. In a statement, the PKK said the attack avenged how Kurds are treated by authorities, particularly in jail.
The militants had planted the explosives and left the base safely, PKK said.
DHA news agency reported that five people had been detained in connection with the incident.
In November, the Kurdistan Workers' Party rebel group was accused of carrying out a car bomb attack at the same police headquarters, in which nine people were killed and dozens and injured.
On Sunday, Turkey will vote in a key referendum on granting President Recep Tayyip Erdogan additional powers.