Madrid, Spain (CNN) -- Police early Tuesday arrested 34 people suspected of belonging to the leadership of a youth wing of the outlawed Basque separatist group ETA, Spain's Interior Ministry said in a statement.
The youths detained would not yet be members of ETA, which is blamed for more than 800 deaths, but are suspected of militant activities to promote Basque independence and which later could lead to them become full-fledged ETA members, reported CNN partner station CNN+.
The arrests occurred in four northern provinces with Basque roots. Police detained many of the suspects near the largest Basque cities of Bilbao and San Sebastian.
Police this year have arrested about 70 ETA suspects in Spain and France, ETA's traditional rearguard base just across the border, Spain's interior minister said last month.
That includes the arrest last month of a suspected top ETA leader, the fifth time since May 2008 that a suspected ETA chief operative has been detained.
ETA is an acronym for Euskadi ta Askatasuna, which means "Basque Homeland and Liberty" in the Basque language. ETA was founded in 1959 and is listed as a terrorist group by the United States, Spain and the European Union.
With ETA seemingly on the defensive, the arrests Tuesday, for suspected membership in the outlawed youth organization known as SEGI, were aimed at preventing the re-energizing of ETA's base, the Interior Ministry statement said.
"This illegal organization (SEGI), besides being the training ground for the terrorist group, is also mandated by ETA to carry out destabilization through so-called street violence," which includes bus burnings and fire bombings, the ministry statement said.
Hundreds of police officers participated in the investigation and raids, and they searched 46 homes and 21 youth centers, seizing pro-ETA publications, material to make firebombs -- including instruction manuals -- and computers, the ministry statement said.
The suspects were to be taken to Madrid for court appearances in the coming days.