A French prosecutor says seven masked men carrying iron bars were arrested overnight in northern France after an attack on migrants near the city of Calais.

Prosecutor Eric Fouard told Le Parisien newspaper that the men aged 24 to 44, several from the area, were in police custody Thursday after their arrest in Loon-Plage. They are accused of attacking four Iraqi Kurdish migrants.

Advocates for migrants in the Calais region say attacks are growing in frequency and severity. The Legal Center, which has offices within the Calais shantytown, blames both police and right-wing groups and says several hundred people have been injured.

Tensions have risen in the region, home to 4,000 migrants camped in hopes of sneaking across the Channel to a better life in England.