In a statement sent to the media, the office of the prime minister, António Costa, said that in view of the forecast of higher risk of fires, particularly over the weekend, in the districts cited, "the government, by decree of the prime minister and the minister of internal administration, will declare a state of public calamity with preventive effects in those parts of the nation's territory."

For Friday, the statement added, Costa and the minister, Constança Urbano de Sousa, have called a meeting with the head of the armed forces, the general commander of the national guard (GNR), the national commander of rescue operations and the president of the Portuguese fire fighters' league, with a view to mobilising as many resources as possible and getting them in place in advance in the areas at greatest risk.

The government is also to be in touch with the mayors of the affected areas so as to identify other preventive measures that should be adopted, the statement said.

The public calamity is a legal state in which special rules apply for the hiring of labour by public sector bodies, as well as guaranteeing "free access" for civil defence forces to private property, and other measures.

It is foreseen in Portugal's basic law on civil defence, which states that it may be declared "in the face of the occurrence of danger of occurrence" of a serious accident or catastrophe, and includes a "special rules on public hiring of public works contractors, supply of goods and acquisition of services".

The declaration of a state of calamity does not alter the obligation of insurers to pay up when clients make valid claims, a spokesman for the Portuguese Insurers' Association said on Thursday.