Three people have died as wildfires raged in the city of Funchal, on the Portuguese island of Madeira.
All three are said to have been elderly people whose homes caught fire. A thousand people have evacuated from homes and hotels.
Fires have also been blazing on the mainland and there are reports of a fourth death in central Portugal.
The government has triggered the EU Civil Protection Mechanism, which enables other European states to help.
Italy has already released a Canadair aircraft to join the effort.
Several arrests have been made of people suspected of illegally starting fires.
Forest fires first took hold in the Portuguese mainland on Friday and on the island of Madeira, off the north-west African coast, on Monday, following weeks of dry weather and temperatures above 35C.
On Tuesday the flames encroached on Funchal, home to some 112,000 permanent residents and capital of an island that attracts more than a million tourists per year.
"Last night, the fire was 100m [330 feet] away from the hotel and you could hear gas bottles exploding," Ricardo Correia, a manager at the hotel Castanheiro, told AFP news agency. "We evacuated our 140 guests as a precaution," Mr Correia said, explaining they had spent the night in a sports stadium.
An iconic hotel on Funchal's outskirts, the five-star Choupana Hills, was gutted by the flames.
Regional President Miguel Albuquerque told a news conference that the fire was still burning on several fronts but was "under control," AFP reported.
"The situation is complex but not catastrophic," he said.
President Marcelo Rebelo de Sousa and Prime Minister Antonio Costa have scheduled a visit to the island on Thursday.
On the mainland, firefighters were said to be exhausted after days battling the blazes.
In addition to three deaths in Madeira, a fourth death was reported - a man aged between 40 and 50 in the central region of Santarem.
There were 176 active fires burning on Wednesday afternoon, according to Portugal's civil protection agency, with 13 causing particular concern - mainly in the north-west of the mainland:
- In Agueda, the fire chief appealed for air support in the face of what the mayor said was the worst fire the area had ever experienced, reported Diario de Noticias (in Portuguese)
- In Arouca, and Aveiro, large blazes were reported after strong winds fanned the flames
- Further north, homes were coming under threat in Santa Maria da Feira, reports said
- Some main roads have also been closed
More than 4,200 emergency workers are battling the flames across the country.
Firefighters are said to have blamed poor forest management for the fires, but President Rebelo de Sousa reportedly insisted the country had been well prepared.