At least two small bombs have exploded along highways in northern Spain shortly after authorities received a phone call warning that at least four bombs had been planted along roads.

Authorities report little damage and no injuries in the blasts, which followed a telephone call by someone claiming to represent the Basque separatist group ETA warning about the bombs.

Thursday's incidents come one day after an explosion outside the offices of the right-wing Falange political party in the northern town of Santona.  They also coincide with a general strike called by an outlawed Basque political party to protest the deaths of two ETA prisoners last week.

ETA has been blamed for more than 800 deaths during a four-decade-old campaign for an independent Basque homeland in northern Spain and southwestern France. 

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