At least one small explosive device detonated Wednesday along a route used by the Tour de France cycling race in northern Spain, a Spanish interior ministry source said.
An anonymous caller claiming to speak in the name of the Basque separatist group ETA had warned highway authorities earlier that the Spanish leg of the race might be targetted with several explosive devices, the Basque news agency Vasco Press reported.
No injuries were reported and the race was not called off.
Government officials were not immediately available for comment on the report that ETA had issued a warning.
ETA, which has killed more than 800 people in four decades of armed struggle for traditional Basque lands in northern Spain and southern France, called off a 15-month ceasefire in June.
The Europa Press news agency reported that two minor explosions had occurred while Vasco Press said only one explosion took place, about 50 metres from the road.