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. The police operation early Tuesday prevented "a great deal of pain and suffering," Rubalcaba said. The police also seized guns, explosives, timers, detonators and computer equipment in the Pamplona raid, the ministry said in a statement.