A 17-year-old pupil has been arrested in Pyrgos, in the Peloponesse, after throwing a homemade explosive device into a classroom.
No one was injured in the blast which caused material damage.
Police said the pupil had constructed the device using instructions found on the Internet.
Local reports said the 17-year-old was “trying to impress” his fellow pupils.
No more details were made immediately available.