Two small devices exploded near the Spanish resort of Malaga on Sunday and police closed a key road looking for a third, but authorities added that nobody had been hurt by the blasts after receiving a bomb warning.
Police had to clear a packed beach in Malaga before the first explosion at around 1 p.m. (1100 GMT) and later had to move what Spanish media said were thousands of people from a marina in the nearby town of Benalmadena before the second blast at 3 p.m.
"Two devices exploded, in Benalmadena and on Guadalmar beach in the (provincial) capital. They were of little power and did not cause injuries or physical damage," said a spokeswoman for the office of the central government in Malaga.
The website of El Mundo newspaper quoted security sources as saying the telephone caller claimed the attacks on behalf of Basque separatist rebels ETA, but the spokeswoman said she did not know of any claim.
Meanwhile, police closed Spain's main coastal motorway while they hunted for a third device somewhere between Malaga and the Costa del Sol resort of Torremolinos, an interior ministry spokesman said.
The incident triggered travel chaos on what is traditionally one of the busiest weekends of the year on Spanish roads.
Last month ETA exploded four small bombs at popular seaside resorts in the north of the country, marking the start of its usual summer bombing campaign to disrupt one of the most important sectors of the Spanish economy.
ETA has killed more than 800 people in four decades of armed struggle for Basque independence from Spain. Spanish Prime Minister Jose Luis Rodriguez Zapatero broke off talks with ETA in December 2006 after its rebels set off a bomb that killed two people at Madrid airport.