A small explosion hit popular Christian pilgrimage centre Santiago de Compostela today after a telephoned warning in the name of armed Basque separatist group ETA.
There were no injuries in the northwestern Spanish town but police were also hunting for a bomb around the seafront of the nearby city of La Coruna.
The blast appeared to be the latest in a series of ETA attacks aimed at Spain's summer tourism business, marking a renewed campaign by ETA after a long period of silence.
Santiago attracts tens of thousands of devout pilgrims to what is traditionally believed to be the burial place of Apostle Saint James, but also draws many other visitors with its medieval sites and beautiful scenery.
Numbers are particularly high this summer because it is a holy year, when the saint's day falls on a Sunday, meaning extra indulgence for the religious and special events for non-believers.
The bomb exploded in the city's Alameda Park, but police had already cordoned off the area so damages were minimal, anti-terrorist sources said.
Seven other small bombs have exploded at holiday resorts on the country's northern coast in August, causing only a few minor injuries.
An anonymous caller rang Gara newspaper, which often receives warnings of ETA attacks, about half an hour before the midday explosion saying two bombs had been placed.
Spanish media reported that police suspected the detonator in the second bomb may have failed. ETA regularly stages summer bombing campaigns aimed at undermining tourism, a pillar of the national economy, although few tourists are scared away.
ETA has killed nearly 850 people since 1968 in a bombing and shooting campaign for an independent Basque state in northern Spain and southwestern France.
Spain, the United States and the European Union consider it a terrorist organisation.
Police have arrested some 650 suspected members of the organisation since 2000 and the number of ETA killings has fallen from 23 in 2000 to three last year.