Nearly 3.5 tonnes of arms, explosives and other materiel have been found in eight arms dumps identified by ETA, French Prime Minister Bernard Cazeneuve said Saturday, following the Basque separatist group's vow to disarm. 

"The French government welcomes this operation, carried out calmly and without violence," Cazeneuve said in a statement.

"It's a decisive step towards the end of Basque separatist terrorism."