Spanish police on Tuesday detained four alleged members of the armed Basque separatist group ETA who are suspected of planning an attack in the country's north, the Interior Ministry said.

The suspects — a woman and three men — were found in possession of arms and explosives. Police believe they were planning an attack in the Navarra region, Interior Minister Alfredo Perez Rubalcaba said.

"Those detained had arms and explosives, which means we are dealing with a cell that was about to attack," Rubalcaba during a news conference in Parliament.

Authorities say ETA has killed three people this year, and more than 825 people since the late 1960s when it began waging its violent campaign for an independent Basque homeland in northern Spain and southwestern France.

The police operation early Tuesday prevented "a great deal of pain and suffering," Rubalcaba said.

The three male suspects — Xavier Rey Urmeneta, 26, Aurken Sola Campillo and Sergio Boada Espoz, both 29 — were detained in Navarra's capital of Pamplona and the neighboring village of Anorbe. Police seized guns, explosives, timers, detonators and computer equipment in the Pamplona raid, the ministry said in a statement.

The fourth suspect, Araitz Amatria Jimenez, 26, was arrested in the eastern coastal city of Valencia, it said.

This year ETA claimed responsibility for the deaths of a former town councilor and a Civil Guard. It is also blamed the killing of an army officer last month.