The 27-year-old is currently third on 1050 points, just 16 behind Russia's Alexander Legkov, who finished eighth in the men's 15km on Sunday, and 123 behind overall leader Dario Cologna who did not compete due to illness.
Northug's time of 34:35.6 minutes was 31.7 seconds better than second-placed Alexey Poltoranin of Kazakhstan, who is hot on the heels of the Norwegian in fourth place overall.
Martin Johnsrud Sundby rounded off the top three with a time of 35:10.7 but is some way off the pace in the standings.
In the women's 10km Poland's Justyna Kowalczyk came out on top with a time of 25:38.9, taking her lead at the top to an almost unassailable 581 points.
The 2010 Olympic champion beat off three Norwegian competitors with Marit Bjoergen in second 23.1 further back, Heidi Weng in third 25.5 adrift and Therese Johaug 28.2 off the pace.