Paris St Germain forward Kylian Mbappe has been ruled out for three weeks after he suffered an ankle injury in Friday's French Cup final win over St Etienne, the Ligue 1 champions said on Monday.

It means Mbappe will miss PSG's Champions League quarterfinal against Italian side Atalanta in Lisbon on August 12.

"The results of today's scan confirmed an ankle sprain with damage to the external ligament. The player is expected to be sidelined for approximately three weeks," PSG said in a statement.

A rough tackle from Loic Perrin saw the St Etienne defender catch Mbappe on the ankle and the 21-year-old collapsed on the pitch in pain before being substituted.

Perrin was sent off for the challenge as PSG won 1-0.