France Under-18 international Medhi Narjissi is missing after being "swept away by a wave" while swimming in the sea off Cape Town, the French Rugby Federation said.

The FFR said the incident took place during a recovery session with other players in South Africa on Wednesday before search teams were immediately dispatched.

Two sea rescue boats and a helicopter were involved but did not find the 17-year-old, who has recently signed for Toulouse.

The search continued on Thursday as National Sea Rescue Institute spokesman Craig Lambinon said strong rip currents could have swept Narjissi into the surf zone and out to sea.

Narjissi is a member of the France squad preparing to participate in a five-nation tournament from Monday, also involving England, Ireland and Georgia.

South African rugby leaders sent condolences to the FFR and the player's family, who were expected to arrive in South Africa later on Thursday.

"We extend our deepest condolences to the family and the French rugby community for the tragic loss of Medhi," said Mark Alexander, president of the South African Rugby Union.

"We cannot begin to comprehend the sorrow the family must be feeling at this moment. Please know that the entire rugby fraternity stands with you in mourning the loss of Medhi.

"This devastating news has been felt deeply across the rugby community here in South Africa and around the world."