DOBBIACO, Italy -- Olympic champion Petter Northug Jr. of Norway took the overall lead in the Tour de Ski after winning Thursday's 35-kilometer free pursuit cross-country race.
Northug surged ahead from a four-man lead group on the final uphill section of the fourth stage from Cortina to Dobbiaco, near the Austrian border, and won in 1 hour, 16 minutes, 32.7 seconds.
Alexander Legkov of Russia finished second, 0.7 seconds behind, and two-time defending champion Dario Cologna of Switzerland was third.
Previous leader Maxim Vylegzhanin of Russia was fourth.
Northug finished second overall three of the past four years and is seeking to become the first Norwegian to win the weeklong event. He holds a 5.7-second lead ahead of Legkov.
In the 15-kilometer women's race, three-time defending champion Justyna Kowalczyk of Poland won in 37:15.1. Charlotte Kalla of Sweden was second, 18.3 seconds behind and Therese Johaug of Norway was third.
Kowalczyk entered the stage with a 50.3-second lead on Johaug, but is just 23.0 ahead of Kalla.
Stage five on Friday features a 5-kilometer classical race for men and a 3-kilometer event for women.
The race ends Sunday with the traditional climb up Mount Cermis in Val di Fiemme.