Therese Johaug dominated the women's five kilometres test on another day of Norwegian success at the International Ski Federation (FIS) World Cup in Ruka, as Martin Johnsrud Sundby won the men's 10km event.
Johaug, a seven-time world champion who also won an Olympic relay gold at Vancouver 2010, finished in 11min 23.8sec in the free technique interval start format today in the Finnish resort.
This put her 17.6 seconds clear of Swedish rival Charlotte Kalla, with Kalla's compatriot Ida Ingemarsdotter a further eight seconds back in third.
Johaug's victory means she leads the three-stage mini tour by the slenderest of 0.4 second margins from team-mate Ingvild Flugstad Oestberg ahead of tomorrow's finale.
"It was a really good race from me," she admitted afterwards.
"A 5km skate was not my distance before.
"I have been working many years on improving my speed and technique.
"I also did a lot of strength training, and it is fun to see it pay off in competitions."
In the men's event, Sundby gained his fifth successive World Cup victory over the 10km distance, finishing 11.2 seconds ahead of Alex Harvey of Canada.
Swiss star Dario Cologna placed third.
Sundby also moved into the overall Tour lead ahead of tomorrow's 15km classic pursuit finale, 13.8 seconds ahead of his team-mate Finn Hagen Krogh
"I have a good start position for tomorrow," he said.
"It will be a new experience to start first in the last stage.
"I have to mentally prepare for that.
"But I think I am in a good shape."
November 2015: Norway at the double as FIS Cross Country World Cup season opens in Finland
March 2015: Norway at the double at cross country sprint World Cup season finale
March 2015: Bjørgen cements position as overall leader with another Cross Country World Cup gold
March 2015: Chaotic conclusion sees Germans take Nordic combined victory in Lahti
March 2015: Northug closes FIS Nordic Ski World Championships with fourth gold