Stabaek wasted the chance to extend their lead at the top of the Tippeligaen after losing 2-1 away to Valerenga on Sunday.
Bojan Zajic put the hosts ahead but Gomes da Costa Alanzinho equalised for Stabaek in the 37th minute. Daniel Fredheim Holm then scored what proved to be the winner on the stroke of half-time.
Stabaek remain two points ahead of Fredrikstad, who have a game in hand.
Third-placed Lyn Olso kept up the pressure on the top two by beating Lillestrom 2-1 courtesy of an early brace from Espen Hoff in the fifth and eighth minutes.
Olivier Occean pulled one back in between that double as the game got off to a blistering start but it turned out to be in vain.
Molde beat Ham-Kam 2-0 with a goal in each half from Mame Diouf (25) and Jose Roberto Mota (74), while Tromso also saw off Stromsgodset 2-0 thanks to late efforts from Sigurd Rushfeldt (84) and Morten Moldskred (90).