Chile has declared a red alert for three national parks and reserves where massive wildfires are threatening forests that are thousands of years old, officials said Tuesday.

The fires have been raging for more than a week in the southern region of La Araucania, which has been hit by a severe drought.

The National Emergency Office (ONEMI) warned they would likely spread and intensify.

"It's going to be difficult to contain this fire today and tomorrow, but we hope that by Thursday we can effectively have it under control," said the vice minister of the interior, Madmuh Aleuy.

The head of national forest service CONAF, Aaron Cavieres, said firefighters were battling to keep the blaze away from populated areas.

"High temperatures and strong winds of more than 50 kilometers (30 miles) an hour are complicating our work to contain the fires," he said.

The fires are burning in three protected areas: China Muerta National Reserve, Nalca Lolco National Reserve and Conguillio National Park.

They have burned more than 5,700 hectares (14,000 acres) of parkland so far, including more than 300 hectares in Conguillio, an Andes mountain park popular with tourists because of its volcanos and centuries-old monkey puzzle trees.

The trees (Araucaria araucana), members of the pine family, can live for more than 1,000 years and grow as tall as 50 meters (165 feet). They are considered sacred by indigenous Mapuche people, and Chile has declared them part of its unique natural heritage.

Environmentalists have warned that the fires are threatening hundreds of plant species and animal life.

The head of environmental group Accion Ecologica, Luis Mariano Rendon said at the weekend it was a "massive environmental catastrophe."

CONAF said firefighters would begin spraying some areas with a chemical flame retardant to create firebreaks.

Three planes and four helicopters are backing up 200 firefighters in the area, some 700 kilometers (450 miles) south of the capital Santiago.

But strong winds prevented the planes from taking off Tuesday.

Thirty Argentine firefighters joined the effort in the neighboring country. Chile has also reached out to Brazil and Uruguay for help, Aleuy said.

In all, 99 forest fires are raging in five Chilean regions. They have burned nearly 20,000 hectares, CONAF said.

Chilean authorities say climate change is causing more forest fires in the South American country, which has seen a decline in precipitation and an increase in temperatures.