The nematodes were first detected in Portugal in 1999 and have spread at an alarming rate, prompting the European Union to offer Portugal some 8 million euros to control the plague in recent years. There is no cure for the infestation.

The new outbreak was detected recently in central Portugal when the organisms began to spread in the warm spring weather.

"The government measures managed to control the nematode in the southern region of Setubal," Agriculture Ministry spokesman Mario Ribeiro said on Wednesday. "But ... in one of our routine analyses, we found a new outbreak in two areas in the centre of the country."

The ministry said the affected areas were in the Arganil and Lousa municipalities, in one of Portugal's largest wild pine forest regions.

It said in a statement it would take measures to fight the infestation in an area totalling 6,500 hectares and would ask landowners to destroy any infected trees to stop it from spreading further.

"The nematode has no cure so we are doing what experts told us to. We are carrying out analysis and asking landowners to take down the trees if they are infected," said Ribeiro.

Asked if there was a risk of the organisms spreading to neighbouring Spain, Ribeiro replied: "there is no answer for that. Everything that is agreed to be done is being done."

Portugal informed the European Union of the new outbreak last week, Ribeiro said. The EU has not taken any measures that would affect Portugal's timber industry exports, he added.

Portuguese exports of cork, pulp and pine wood are worth about 2.5 billion euros a year. About half a million pine trees were felled when the forest corridor was cleared last year.

Recent droughts in Portugal are believed to have weakened the trees' natural defences against the nematodes.