Madrid (CNN) -- Spanish police seized a total of 1,600 kilos of bomb-making materials this week from suspected ETA hideouts -- the largest haul ever against the Basque separatist group in Spain.
Authorities also arrested three ETA suspects this week -- including one during a seizure on Thursday -- in the latest actions in a police crackdown against ETA despite its unilateral cease-fire declared last January 10.
The Spanish government has vowed to keep up the pressure on ETA because the outlawed group, listed as a terrorist organization by the European Union and the United States, has broken cease-fires in the past.
The police on Tuesday arrested two men in northern Spain suspected of supplying explosives and bomb-making materials to ETA. A search of their property turned up 850 kilos (1,870 pounds) of bomb-making components.
Then on Thursday, the police discovered another 750 kilos (1,650 pounds) of explosives and components at various suspected hideouts, and arrested a third suspect. The two seizures totaled about 3,520 pounds.
ETA is blamed for more than 800 deaths in its long fight for Basque independence, many of those due to car bombs and package bombs.
Last month in France, police arrested the suspected military chief of ETA, in charge of commandos who carry out the bombings. In recent years, the police have arrested in succession a series of suspected ETA military chiefs as ETA replacements step in to fill the vacant position at the top.
Also last month, in northern Spain, police arrested four key ETA suspects who authorities said had tried to operate under police radar, carrying on ostensibly law-abiding lives but secretly working for ETA. Police seized 200 kilograms (440 pounds) of explosives in those raids.
Top government officials have said ETA appears to be weaker than ever, but they have warned that the group still has the capacity to kill.
The Socialist government and the main opposition conservative party have said ETA's current unilateral cease-fire is not enough, and that only a commitment to permanently end the violence and lay down weapons would suffice.
Deputy Prime Minister Alfredo Perez Rubalcaba said last month, "The government's anti-terrorist policy has not changed at all because ETA has not definitively abandoned its weapons. And as long as it doesn't, the police will continue to arrest them, one after another."