The club said the Spanish 23-year-old will soon undergo surgery for the injury, which occurred just minutes after he scored an equalising goal in Real's win over Arsenal in the United States on Tuesday.

"After tests carried out on our player Marco Asensio by the Real Madrid Medical Services he has been diagnosed with a rupture of the anterior cruciate ligament and the external meniscus of his left knee," the club said in a statement.

"The player will be surgically operated on in the next few days."

Spanish media reported that such an injury would rule him out for six to eight months.

Real had been down 2-0 to Arsenal at half-time, but Gareth Bale pulled one back in the 56th minute before Asensio drilled the equaliser three minutes later.

However minutes after his goal Asensio took an awkward step and immediately clutched his left knee and fell to the ground.

He was stretchered off in agony in the 65th minute.

The Arsenal match finished 2-2, and Real prevailed 3-2 in the penalty shootout dictated by the International Champions Cup exhibition tournament format.

Spanish media reported that Asensio's injury could affect the future of his teammate Dani Ceballos, who was reportedly close to being traded to Arsenal.

However the Spanish club, which is also looking to part with Bale, could now hold on to midfielder Ceballos.