The 20-year old Italian had a share of the first-round lead with Pablo Larrazabal and shot a round of 7-under 65 to move on to 13-under on the Bro Hof Slott course.
"It was nice after my good start to come back today and shoot another great score," he said.
"I am glad the way the day has gone as I played solid. Over the last five or six holes I didn't feel as good as I did at the beginning but I was scoring well which is a good sign."
Finn Mikko Ilonen stands second after shooting a blistering 63 - birdying his last three holes - to match a course record set by Peter Whiteford just hours earlier.
The Scot is third on 10 under after a personal-best round in five seasons on the European Tour.
"It was brilliant and a great round of golf, and it's put me in a good position though it's still a long way to go," Whiteford said.
"The scoring looks like it will be low over the weekend but it's just great to be in contention again."
He lost a play-off for the Ballantine's Championship in South Korea a month ago.
Spain's Larrazabal dropped to tied-for-fifth after following up a 66 with a 70, with Dutchman Joost Luiten fourth.
Manassero claimed his fourth European Tour title at the PGA Championship last weekend. He is bidding to become the first player to win consecutive European Tour titles since Branden Grace at the beginning of the 2012 season.
Scot Marc Warren, who was involved in that play-off at Wentworth, missed the cut in Sweden, as did Darren Clarke