A forest fire raging in southwestern France was again advancing on Sunday afternoon because of strong winds, even as efforts to put out one of the country's worst fires in five years were considerably stepped up.

The fire, which erupted Friday afternoon and spread quickly because of strong winds, has now consumed nearly 550 hectares (1,360 acres) -- the equivalent of about 550 rugby fields -- of pine forest on the western edges of the city of Bordeaux.

Some 650 firemen and other forces have been deployed, among them reinforcements from across France, as Interior Minister Bernard Cazeneuve visited the firefighters' operations centre on Sunday morning.

Seven firefighting planes backed up ground efforts Sunday afternoon.

However winds at up to 50 kilometres (30 miles) per hour were fanning the flames, police official Pierre Dartout said.

"The fire has advanced again," he warned.

"It's a complicated fire," local fire chief Jean-Paul Decellieres said.

"It resurges depending on the direction of the wind," he added, warning it may take several more days before the fire is put out.

The causes of the fire remain unknown though a police investigation is underway.

Much of France is experiencing a drought and several fires broke out Friday in the pine forests that dominate to the west and south of the city Bordeaux.

The region's celebrated vineyards are located mostly to the east and north of the city, with national authorities saying the hot and dry weather has so far favoured the growth of grapes, though the harvest is expected to dip slightly from last year.