MADRID, July 22, 2008 (AFP) - Spanish police dismantled the armed Basque separatist group ETA's most active unit with the arrest Tuesday of at least eight suspected members of the group in raids across the country.

Among those captured was Arkaitz Goikoetxea, the alleged leader of the 'Vizcaya' cell which Spanish police suspect was behind a string of recent bombings, Basque news agency Vasco Press reported.

Goikoetxea was detained at an apartment in Bilbao, the financial capital of Spain's northeastern Basque region, in an early morning raid, it said.

The 'Vizcaya' unit carried out 80 to 90 percent of ETA's attacks since the group called off a ceasefire in June 2007, the editor-in-chief of the Bilbao-based news agency, Florencio Dominguez, told AFP.

'This operation deprives ETA of one of its main tools,' added Dominguez, who is an expert on ETA.

The interior ministry would not confirm the number and identities of those arrested, saying only that an operation was underway. Interior Minister Alfredo Perez Rubalcaba was to hold a news conference at 1:00pm (1100 GMT).

ETA, whose symbol is a snake wrapped around an axe, has killed over 820 people in its 40-year campaign of bombings and shootings to carve a Basque homeland out of northern Spain and southwestern France.

The latest police operation is seen as the biggest blow against ETA since the group's presumed leader, Javier Lopez Pena, was detained along with three other suspected members of the group in France in May.

Police believe the 'Vizcaya' unit was behind five car bombings carried out over the past year, including one of a police barracks Legutiano that claimed the life of one officer.

The unit is also suspected of being responsible for the four weak bombs which exploded at two seaside resorts on Sunday in the northern province of Cantabria following a warning call from ETA.

The explosions in Laredo and Noja caused slight material damage and slightly injured a woman who was struck by a rock that was sent flying by one of the blasts. A pregnant woman was also treated for shock.

ETA, whose initials stand for Euskadi ta Askatasuna, or Basque Homeland and Freedom in the Basque language, is considered a terrorist organisation by the European Union and the United States.

The group declared a 'permanent' 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.

Spain's socialist government has adopted a hardline against ETA since the group lifted 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.