The suspected arsonists, men aged between 20 and 40, were arrested during the past month. Police believe up to a third of all forest fires were deliberately started.

Firefighters are tackling 10 forest fires across the centre and north of Portugal, with authorities declaring an orange alert – the second highest fire level.

Meanwhile, across the border in Spain a third person has died in forest fires. About 79 fires have affected more than 5,000ha in the north-west of the country.