Four bombs exploded at popular seaside resorts in Cantabria northern Spain on Sunday, after warning calls from the Basque separatist group ETA and following a small explosion outside a Barclays bank near Bilbao.
One woman was hurt by a flying stone and another treated for shock.
The attacks, which marked the beginning of ETA's traditional summer bombing campaign, which targets Spanish holiday resorts as part of the group's four-decade struggle for an independent Basque state in northern Spain and southern France.
Spain's Socialist government says the guerrillas have been severely weakened by a string of arrests, and have called for their surrender after calling off peace talks two years ago.
Prime Minister Jose Luis Rodriguez Zapatero broke off a peace process with ETA in 2006 after the group killed two Ecuadorians when it detonated a car bomb at Madrid's Barajas international airport.
The government condemned the attacks on Sunday and reaffirmed its commitment to fight the group.
"The best way to get a long prison sentence in Spain at the moment is to join ETA," Spanish Interior Minister Alfredo Perez Rubalcaba told national radio on Sunday after the attacks.
The first Cantabria bomb exploded at about 11:15 a.m. British time on a seafront promenade in Laredo, one of northern Spain's most popular holiday destinations, damaging the walkway, breaking windows and sending a 25-metre plume of smoke into the air, an official said.
Holidaymakers had been cleared from the beach 45 minutes earlier and took cover in local cafes and bars which drew down shutters to protect against the blast, witnesses told radio.
"We received a call at around 10:30 a.m. from someone who said they represented ETA and told us ETA had planted four bombs," said an emergency services official. "There were no injuries because the area had been cleared and cordoned off."
WEAKENED, STILL FIGHTING
Many European schools have started, or are beginning to start their summer holidays and ETA's summer bombings are aimed at hurting tourism in Spain, the world's second most popular holiday destination after France.
The second bomb went off around 40 minutes later next to the lifeguard tower on the beach at Noja, about 19 miles from Laredo, causing a loud blast but no damage, media said.
