LISBON, Portugal — More than 100 wildfires stretched thousands of firefighters to the limit in northern Portugal on Wednesday, with seven deaths since the worst spate of fires in recent years spread out of control over the weekend. Portuguese Prime Minister Luís Montenegro declared a state of calamity for the hardest-hit areas late Tuesday, invoking powers to mobilize more firefighters and civil servants. He also called on police investigators to redouble their efforts to find those who started the fires and pledged help for those who have lost their homes or have been evacuated. “We are well aware that these difficult hours are not over yet,” Montenegro told the nation in a televised address. “We have to continue to give everything we have and ask for help from our partners and friends so that we can reinforce the protection of our people and property.”

Additional coverage in Reuters, by Miguel Pereira and Guillermo Martinez: Beset by wildfires, Portugal gets help from Spain, Morocco