Despite enjoying home advantage Norway had surprisingly lost their two matches against Brazil and Portugal in the opening round and in the first half of the encounter against Spain Norway looked far from their best with 10 turnovers proving costly, and big star Sander Sagosen once again failing to create a proper rhythm for the hosts.
Right backs Alex Dujshebaev and Imanol Garciandia was in fine form for the guests who enjoyed a 13-10 lead at the interval as Norway scored only one goal in the last 11 minutes and 40 seconds of the half.
Spain began the second half where they had left off and extended their lead to 18-13 with 20 minutes left before mainly Tobias Grondahl helped turn the game on its head as the Unity Arena in Baerum became increasigly noisy with the home side gaining momentum.
Norway in the end ran away with a 25-24 win, but the win could come at a great cost as Sander Sagosen suffered a potential tournament-ending injury, as he had to be carried to his bench by his teammates.
Elsewhere Iceland took an impressive win against Egypt (27-24) in their first match in the main round after the two teams had impressed so far by winning their respective preliminary groups in Zagreb. Slovenia got back to winning ways with an expected 34-23 win against Argentina while co-hosts Croatia begain the main round with a bang as they defeated Cape Verde 44-24.