Migrants have clashed with Greek riot police during a protest near the country's border with Macedonia.

The violence in Idomeni comes ahead of the resumption of deportations today as part of a controversial EU migrant-swap deal with Turkey.

Under the agreement Turkey will have one Syrian refugee removed, for every person it takes back from Greece.

The deportations had officially started last Monday, but hit a stumbling block when authorities weren't able to keep up with the numbers applying for asylum.