(BSS/AFP) - Wildfires raging in a forest south of Paris have devoured more land overnight, firefighters said on Tuesday, ahead of France`s national day celebrations.

The fire erupted Sunday in the sprawling Fontainebleau forest some 60 kilometres (40 miles) southeast of the capital, former royal hunting grounds that today are dotted with quiet villages and are popular with hikers and climbers.

A second, smaller fire erupted a day later and the blazes have now scorched more than 1,900 hectares (4,700 acres) -- an area roughly three times the size of Gibraltar, firefighters said on Tuesday.

With some 850 firefighters battling the flames with the help of specialised aircraft, authorities are hoping to gain the upper hand on the flames during the day, said Paul-Edouard Laurain, spokesman for the regional firefighters.

France is on Tuesday celebrating July 14 national day, which is usually accompanied by evening fireworks.

With the region sweltering through its third heatwave in as many months, many towns throughout France have cancelled their annual firework displays, but many are usually set off illegally.

This year`s celebrations coincide with a World Cup semifinal match in which France is taking on Spain in the evening local time and which, win or lose, will likely see fans spilling outside to either celebrate or mourn once the final whistle blows.

The fires have forced some 1,000 people in and around Fontainebleau to flee their homes.

Authorities are probing whether the fires were started deliberately and two people have been arrested on suspicion of arson.

The scale of the fire led to the deployment of four Canadair aircraft -- an unprecedented move in the greater Paris region -- as well as two Dash planes and three water-bombing helicopters.

A total of 187 water drops were carried out by Monday evening, said the commander of the rescue operations, Jean-Marc Sicard.