MADRID — Four bomb blasts claimed by Basque separatists militants ETA struck two seaside resorts in northern Spain Sunday, police said, in a fresh offensive by the group against tourism targets.

Two bombs struck a seafront promenade at Laredo, damaging the walkway and a cabin used by lifeguards and the other two went off in sand dunes and a golf course in Noja some 30 kilometres (20 miles) away, police said.

A woman was slightly injured when she was hit by a rock that was sent flying by the explosion at the golf course, a local government official said. She was treated in hospital and released.

A pregnant woman who was having lunch nearby the golf course was also treated for shock.

Police cordoned off the areas after firefighters received a telephone call warning them that ETA, which has killed over 820 people in its 40-year campaign for an independent Basque homeland, had planted the bombs.

The beaches at Loredo and Noja, located halfway between Santander and Bilbao, are normally packed during the summer but grey and showery weather made them not busy on Sunday.

Earlier Sunday a small blast went off outside a Barclays bank in Getxo, a suburb of Bilbao, damaging a cash dispenser and breaking windows, according to Getxo mayor Imanol Landa. He blamed the attack on Basque nationalists.

The bombings came after Spain’s Constitutional Court on Thursday blocked a plan by regional Basque authorities to hold a referendum on self-determination for the region.

Interior Minister Alfredo Perez Rubalcaba vowed those behind the bombings would be brought to justice.

“In Spain the best way to secure a long prison sentence is to join ETA,” he told reporters.

ETA, which is considered a terrorist organisation by the European Union and the United States, has frequently targeted Spanish holiday resorts in the past.

In 2002, a booby-trapped car bomb exploded near a bus stop, killing two people, including a six-year-old girl, at Santa Pola, near Valencia on the eastern Mediterranean coast.

In July 2003, two simultaneous bomb attacks injured several foreign tourists in Alicante and Benidorm, on the southern coast. Other devices exploded on the northern coast in 2004.

Spain is the second-most visited country in the world after France and tourism is a key sector of its economy.

ETA last struck on July 4 with a small blast at a telecoms relay station in the Basque town of Barrundia.

Prior to that attack, a June 8 explosion rocked the printing press near Bilbao of El Correo, the main Spanish-language newspaper in the Basque region.

Both blasts caused material damage but no casualties.

ETA declared a unilateral ceasefire in March 2006, raising hopes for an end to the violence.

But an ETA bombing at Madrid’s airport in December 2006 that killed two men put an end to tentative peace talks with the government.

The group officially terminated the ceasefire in June last year, and since then the Spanish government has blamed it for four killings including those of civil guards across the French border.

Spain’s socialist government has adopted a hard line against ETA since the group called off the ceasefire, arresting dozens of its members and suspending two pro-ETA nationalist political parties through legal action.

Prime Minister Jose Luis Rodriguez Zapatero meanwhile has ruled out any future peace talks with ETA.

“Dialogue has proved useless, seeing what ETA has done. There is not going to be dialogue,” he said in an interview published last month in top-selling daily newspaper El Pais.