At least four bombs have exploded in cities in Spain during the past hour, shortly after the outlawed Basque separatist group ETA said it would detonate multiple explosive devices.

ETA telephoned an advance warning of its plans to a Basque newspaper.  Authorities cordoned off all of the group's intended targets, on streets, open plazas and parking lots.  Reports are still coming in from the scene of the blasts, which occurred simultaneously.

Today is a public holiday in Spain marking the 26th anniversary of the national constitution's passage in 1978.  The constitution forms the basis of Spain's policy of granting autonomy, but not outright independence, to regions such as the northern Basque country.

Some information for this report provided by AFP, AP and Reuters.