A bomb exploded today outside a factory in the Basque city of Bilbao after a warning call from the separatist group Eta, Basque police said.
There were no reports of injuries.
It was the third bombing in a week attributed to or claimed by Eta, further undermining recent hopes that the armed group was on the verge of declaring a truce.
The bomb was placed outside a cannery in Bilbao, authorities said.
Police had cordoned off the area after the Basque newspaper Gara said it had received a warning call from someone claiming to speak for Eta.