A police officer has been injured after an unidentified explosive device detonated in the center of the Greek capital, Athens, Reuters reports citing local TV ERT.The blast happened just outside Saint Dionysios Church in the Kolonaki district. "The police officer spotted a box outside the entrance of the church and thought it was strange. The blast was not powerful, the officer was injured in the face and hands," a law enforcement representative told Reuters. The officer has been admitted to hospital, it is reported, and the area was sealed off.