Wanyama rejoins old boss Pochettino at Spurs

The 24-year-old Kenyan international, who Southampton refused to sell to Spurs last year, will cost a reported £9 million ($13.4 million, 11.7 million euros), although with add-ons it could rise to £12 million.

Wanyama signed a five-year contract and is Pochettino's first signing of the close season, as he builds a side not only for the Premier League campaign but also the Champions League after they finished third last term.

Wanyama said in an open letter that he was sad to leave the club that in 2013 gave him the chance to become the first Kenyan to play in the Premier League.

"I write to you with a heavy heart to announce that I will be leaving Southampton Football Club," he said.

"As you can imagine it is very emotional for me to say goodbye to the club that gave me the chance to be the first Kenyan to play in Premier League.

"Firstly, I would like to thank the most important part of every club, the fans. It took a while for me to win you all over but I can truly say that with your support and affection I have grown as a player and a person.

"I will never forget my time in Southampton Football Club, I will keep the club forever in my heart."

Wanyama, who made his international debut aged just 15, impressed for the Saints last season as they finished a best-ever sixth in the Premier League.

Wanyama, who scored four goals in 85 league appearances and had a year to run on his contract, is the second big loss to Southampton in the past week after manager Ronald Koeman left to take over at Everton.

Pochettino was the man responsible for bringing Wanyama to Southampton, signing him from Celtic for the 2013/14 campaign but the Argentine left for Spurs at the end of that season.