LONDON, June 6 (Xinhua) -- English Premier League giant Manchester United announced on Wednesday that they have signed Diogo Dalot from Porto on a five-year contract, with an option to extend for a further year.

The 19-year-old Portugal under-21 international came through the ranks of Porto's youth system. He made his debut in Portugal's Primeira Liga earlier this year.

Dalot, who has made seven senior appearances for Porto, said that "joining Manchester United is an unbelievable opportunity."

"The chance of coming to the biggest club in the world is something I just couldn't turn down. I'm excited about working with Jose Mourinho and learning everything I can from such a successful coach. I am looking forward to playing alongside the fantastic players in the squad," Dalot added.

Manchester United manager Mourinho praised Dalot.

"Diogo is an extremely talented young defender with all the qualities to quickly become a great player for this club. He has all the attributes that a full back needs: physicality, tactical intelligence and technical quality, combined with a Porto academy mentality which prepares players for the maturity they need at the professional level. In his age group, he is the best full-back in Europe and we all believe he has a bright future ahead of him at Manchester United," Mourinho said.

Dalot is United's second signing of the summer, after they agreed to a deal for Shakhtar Donetsk's Brazil midfielder Fred on Tuesday for a reported 47 million pounds (about 63.4 million US dollars).