LISBON: Portugal's Interior Minister Constanca Urbano de Sousa resigned Wednesday as criticism mounts over the government´s handling of a series of deadly forest fires that killed more than 100 people in four months.

Socialist Prime Minister Antonio Costa accepted her resignation, his office said.

On Sunday, a series of deadly wildfires broke out in the centre and north of the country which killed 41 people and injured another 71, the civil protection agency said.

Similar huge blazes in June killed 64 people and injured 250 near the central Pedrogao Grande region, in what were the deadliest wildfires in the country´s history.

As the toll mounted on Monday, a small rightwing party had called for the minister to step down. Costa initially resisted the demand but by Wednesday appeared to have backed down.

After the tragedy in June, the government came under mounting criticism for failing to develop a coherent strategy to fight forest fires, which has further sharpened over its inability to prevent another devastating disaster this weekend.

On Tuesday evening, hundreds gathered in Lisbon under the pouring rain to demonstrate their anger over the government´s failings, shouting "Shame!" and "Resign!" in a protest organised through Facebook.

"A hundred people are dead and nobody is taking responsibility... We need answers!" one demonstrator said on national television.

On Monday, Costa reaffirmed his pledge to prevent new tragedies by carrying out "fundamental reforms" in forest management and firefighting.

But a day later, conservative President Marcelo Rebelo de Sousa called on the socialist government to "bear all the consequences of this tragedy".

The CDS-PP, which had called for the minister´s resignation, has tabled a motion of no confidence in the government over its failure to prevent the fires, but it looks set to be easily overcome by the Socialist majority.

No date has been set for the vote.

"The Assembly needs to clarify whether or not it wishes to keep the government in place," he said, noting that if the motion failed, the government would have a more solid base from which to carry out the necessary reforms.

Portugal on Tuesday began three days of national mourning for the victims.