Seven members of an environmental group in Veria, northern Greece, were arrested yesterday after emptying bags of silt at a conference of local authority leaders to protest the extraction of gravel from the bed of the Aliakmon River.

The ecologists interrupted the meeting – between Central Macedonia Governor Giorgos Tsiotras, the local prefect and 12 local mayors – to protest the “illegal” removal of gravel from the river which, they say, is polluting the water.

The protesters started emptying bags of gravel, or silt, onto the conference table as Tsiotras was making a speech.

Members of the same group had targeted Tsiotras in a similar way in his office last year. This time Tsiotras decided to take legal action against all seven assailants whose actions he described as “the depravities of self-styled ecologists aimed at causing a stir on camera.”