Oberhof, Germany (dpa) - Norway′s Petter Northug won the men′s prologue in cross country skiing′s sixth Tour de Ski, while Poland′s Justyna Kowalczyk began her quest for a hat-trick of Tour titles by triumphing in the women′s race.

World Cup leader Northug posted seven minutes 58.3 seconds in the 4km freestyle race, beating title-holder Dario Cologna of Switzerland by 0.7 seconds. France′s Maurice Manificat was third, four seconds back.

Kowalczyk, seeking a third straight Tour title, took the 2.5km women′s freestyle prologue in 7:03.7, 0.4 seconds ahead of World Cup leader Marit Bjoergen of Norway and four seconds up on Sweden′s Hanna Brodin.

"It was a good race today. Normally I don′t feel good in these kinds of fast conditions but yeah, I′m pretty satisfied," Kowalczyk said.

"My tactic was to not start too fast as I normally have problems with the downhill and my legs were fresh, but I heard my downhill time was quite good and I think that′s the reason."

Bjoergen, starting last, was also pleased with her performance despite just being squeezed out by her rival.

"It′s a good start and it′s good to race again," she said.

The tour, over five different venues in Germany and Italy, takes in a further eight stages finishing on January 8 in Val di Fiemme, Italy.

It continues Friday in Oberhof with the 10km women′s pursuit and 15km men′s pursuit in classic style. dpa bwh