MADRID - A wave of forest fires sweeping through northwestern Spain appear to have been "strategically planned," Interior Minister Alfredo Perez Rubalcaba has said as he visited the region.

On a visit to the Galician regional capital of Santiago de Compostela Rubalcaba said Friday many fires seemed to be "strategically planned with very evil intentions."

Several leading politicians have denounced the apparent deliberate setting of fires, more than 120 of which were raging out of control across the Galicia region Friday as Rubalcaba arrived to assess the situation and consult with firefighters and troops straining to tackle the blazes.

Rubalcaba announced that 20 people had been arrested on suspicion of deliberately starting most of the blazes which have broken out in the past week, up from 14 on Thursday.

According to Rubalcaba, the arsonists "seem to be fully aware of what they are doing" as setting a fire "demands a degree of preparation."

He added the authorities were not ruling out that organised criminal groups were responsible.

Spanish Prime Minister Jose Luis Rodriguez Zapatero flew over the region Thursday to see the damage at first hand amid estimates of some 50,000 hectares (125,000 acres) of land going up in smoke -- double the annual average for this region.