Basque separatist group ETA has reacted angrily to a joint Spanish and French police operation that has seized a cache of hidden weapons.

ETA describes the raid, in which 26 firearms and 50 kilograms (110 pounds) of explosive material were found in the French city of Biarritz on May 28, as an "attack" on its process of eventually disarming.

ETA's statement was published Saturday in Basque newspaper Gara.

The group announced in March 2014 it had begun to store weapons beyond its members' reach, claiming the secretive process would eventually render its entire arsenal harmless.

Spain dismisses the move as meaningless.

ETA seeks to create an independent Basque state in northern Spain and southwest France. It killed about 830 people, mostly in Spain, from 1968 to a 2011 "permanent" cease-fire.