Spanish police have made their biggest seizure of explosives from Basque separatists to date.

According to Spanish authorities, 1.6 tons of explosives were confiscated this week in northern Spain from the armed Basque separatist group ETA.

The seizure comes after police on Tuesday launched an operation against the ETA commando unit known as "Erreka."

"Since the start of the operation against the Erreka commando unit, the Civil Guard seized more than 1,600 kilograms (3,500 pounds) of explosive material in what is the biggest ETA haul found in Spain until now," the statement said.

Suspects in custody

So far, three people have been arrested in the operation - two on Tuesday and one on Thursday.

The Interior Ministry said police found 750 kilograms of explosives in various hiding spots Thursday after acting on information from an ETA suspect detained two days earlier along with his brother.

In their pre-dawn raid on Tuesday, police had found 850 kilograms of ammonium nitrate fertilizer, 13.5 kilograms of the explosive pentrite and detonators on a secluded farm in Legoretta.

Tuesday's discovery was the single biggest explosives cache to be confiscated by police in Spain since 1999.

ETA 'still violent'

ETA, deemed a terrorist organization by the European Union and the United States, is blamed for 829 deaths over the course of its four-decade campaign of bombings and shootings for the an independent Basque state in northern Spain and southwestern France.

In January, the group declared a "permanent and general cease-fire." However, Spanish Prime Minister Jose Luis Rodriguez Zapatero dismissed the declaration out of hand, saying he aimed to see ETA disbanded altogether.

Spanish Interior Minister Alfredo Perez Rubalcaba said Tuesday that ETA had not "definitively given up violence" and that Madrid would continue its efforts to disarm the group for good.

Author: David Levitz (AFP, AP)

Editor: Nancy Isenson