Several key France players, including Real Madrid's Karim Benzema, were injured before the tournament started.

"I am extremely sorry for Lucas," said manager Didier Deschamps.

"We are losing an important element. Lucas is a warrior and I have no doubt he will do everything possible to return to the game.

"On behalf of the group, I wish him the best possible recovery."

The extent of Hernandez's injury was confirmed by an MRI scan on Wednesday morning.

He went down clutching his knee in the 13th minute in the build-up to Australia's opening goal.

Hernandez was replaced by brother Theo, who plays for AC Milan, and France recovered from going behind to take control of the Group D game.

Goals from Adrien Rabiot, Kylian Mbappe and two from former Arsenal and Chelsea striker Olivier Giroud secured a comfortable win.

Ballon d'Or winner Benzema, 34, was ruled out of his country's World Cup defence on Sunday - the opening day of the tournament - as a result of a thigh injury.

He was not replaced, leaving France with 25 players, and Hernandez's injury means Deschamps now has a squad of 24.

Midfielders Paul Pogba and N'Golo Kante were not fit enough to be included in France's original 26-man pool.

Paris St-Germain defender Presnel Kimpembe withdrew last Monday after failing to recover from a hamstring problem and was replaced by Monaco's Axel Disasi.

Two days later, RB Leipzig forward Christopher Nkunku was ruled out after limping out of training, with Eintracht Frankfurt's Randal Kolo Muani called up as a replacement.