Manchester United have reached an agreement for the sale of goalkeeper David de Gea to Real Madrid, Press Association Sport understands.

The deal is yet to be completed but is believed to be worth around £29million with Costa Rica keeper Keylor Navas moving in the opposite direction.

A confirmed transfer would end a long summer of speculation over the future of De Gea, who has been consistently linked with a switch to the Bernabeu.

The 24-year-old Spain international has not played this season due to the uncertainty over his future at United. Manager Louis van Gaal felt the player was not in the right frame of mind to feature amid continuing, but unconfirmed, reports of Real's interest.

The transfer would allow Van Gaal to move on from the situation with Navas, 28, coming in to compete with Argentinian Sergio Romero for the number one spot.

News of the potential deal came on a busy day of transfer activity at Old Trafford.

By the evening the club also seemed to be closing in on a £36million deal for highly-rated France Under-21 international striker Anthony Martial from Monaco. The 19-year-old travelled to Manchester to discuss details after being granted permission to leave the France squad.

While that and the possible De Gea departure were unfolding, there were two other high-profile exits.

Striker Javier Hernandez, who spent last season on loan at Real Madrid, joined Bayer Leverkusen for £7.3million.

Winger Adnan Januzaj, who scored the winner against Aston Villa earlier this month, moved to Borussia Dortmund on loan until the end of the season.

Another goalkeeper was also on the move was Anders Lindegaard, who joined West Brom on a two-year contract after four years spent largely as De Gea's back-up.

The fee for Martial would be a world record for a teenager if confirmed. His arrival would strengthen an attack in which Wayne Rooney appears to have become the only senior out-and-out striker.

Van Gaal is thought to have been tracking the player for some time and United made their move after Monaco failed to qualify for the Champions League group stage last week.

Martial only signed a new contract at Monaco in June, following interest from Tottenham, and was described as "untransferable" by the club at the time.

The size of the fee, however, appears to have prompted a rethink. There has been no confirmation from United but the French Football Federation confirmed discussions were under way.

Martial had been called up to the senior squad for the first time, ahead of friendlies against Serbia and Portugal, but coach Didier Deschamps allowed him to leave camp.

A statement from the FFF read: "Anthony Martial requested permission from Didier Deschamps to travel to England to sign a contract with Manchester United.

"Given the exceptional circumstances, the coach has agreed to the request of the player."