Chile's president has announced that parts of a world-famous national park devastated by forest fires will reopen, even as firefighters continued to battle blazes sweeping through the country's south and central regions.

Sebastián Piñera said on Tuesday about 80% of the spectacular Torres del Paine national park would be reopened to tourists even though several fires continued to rage in its southern section. "As of 8am tomorrow [Wednesday] morning a very important part of the park will reopen," Piñera said, according to the Chile's La Tercera newspaper.

A day earlier, Piñera – whose popularity has slumped to a record low, partly because of what many see as a sluggish government response to the fires – was forced to defend his reaction. Authorities had "provided all the resources requested, even more", he claimed.

"We still have to work for full control of the situation. Unfortunately because of the drought and the heat wave we still have a situation of extreme vulnerability regarding fires," he added.

The worst-hit area has been the Bio-Bio region, around 300 miles south of the capital, Santiago. Authorities said on Wednesday that 171 homes and 28,300 hectares (69,900 acres) of land had been destroyed by fires there, while hundreds had been forced from their homes. Vicente Nuñez, head of Chile's national emergency office, described the Bio-Bio fire as "especially complex".

Fires broke out at the Torres del Paine park – a major tourist destination in Patagonia that tourism officials say receives some 150,000 visitors a year – last Tuesday, spreading to other areas over the weekend. Hundreds of firefighters have been deployed to fight the fires, which have reportedly killed at least one elderly man.

After flying over the park on Tuesday, Chile's economy minister, Pablo Longueira, described the situation as "bleak".

Some have blamed the fire on Rotem Singer, a 23-year-old Israeli tourist. One prosecutor claimed Singer, who was released on Sunday but had his passport confiscated, triggered the disaster after setting fire to toilet paper without putting the flames out. Singer and his family have denied the charges.

"He was a long distance from where the fire began," his father, Hezi, said according to the Haaretz newspaper. "Rotem is confused and frightened. They brought him a translator we know nothing about, and a local attorney who isn't exactly doing his job. They were probably looking for a scapegoat who doesn't speak Spanish."