Firemen working at the Cirque de Mafate on the French overseas island of La Reunion in the Indian Ocean. French authorities sent reinforcements Monday to battle a wildfire raging through the national park of Reunion Island, a unique ecosystem designated a World Heritage Site.

French authorities sent reinforcements Monday to battle a wildfire raging through the national park of Reunion Island, a unique ecosystem designated a World Heritage Site.

A total of 171 firefighters were to arrive on the French overseas territory in the southwestern Indian Ocean, local prefect Michel Lalande said, bringing to 400 the number of French reinforcements sent to help battle the blaze.

The fire erupted on October 11 in La Reunion and according to local officials has already affected more than 2,600 hectares (6,400 acres) of land.

The park, which covers more than 100,000 hectares or 40 percent of Reunion, was last year granted status by UN cultural agency UNESCO, which praised its "variety of rugged terrain and impressive escarpments, forested gorges and basins creating a visually striking landscape".

UNESCO raised concerns about the fire in a statement last week, saying it was "the worst the area has seen in 20 years."

"Key areas of endemic plants seem to be seriously affected as well as other key micro-habitats for biodiversity. Among wildlife, several are under threat," UNESCO said.

French environmentalists have accused authorities of reacting too slowly to the fires.

The French Green Party on Sunday denounced "the drastically inadequate response" by state and to the fire, which it called "a true national catastrophe".