The 18-year-old midfielder has signed a five-year contract, making the move to City on Thursday.
Viana said: “Sverre is an exciting young player that the Club has been monitoring for quite some time now.
“We feel that he already has numerous standout qualities but that at only 18 years of age, he is only going to continue to improve.
“We believe he will be an important asset for Manchester City in the years to come and we will support him every step of the way in his development.”
City and Norway connection
Meanwhile, Nypan said upon putting pen to paper: “I am incredibly happy and proud to have joined Manchester City.
“It’s a dream for any young footballer to become part of this Club and to join such a group of world class talent.
“I am still very young with a lot to learn but the chance to be coached by Pep Guardiola, the best manager in the world, will only help me to become a better player.
“There is already a special connection between Norway and Manchester City through Erling Haaland and Oscar Bobb, and I am very proud to have become the latest Norwegian player to have joined the club.”