Martin Johnsrud Sundby extended his dominant overall lead with victory in Lahti  ©Getty Images

Norway won every medal on offer on skiathlon day at the International Ski Federation (FIS) Cross-Country World Cup in Lahti. 

World Cup leader Martin Johnsrud Sundby came home ahead of compatriots Finn Hågen Krogh and Hans Christer Holund in the men's 30 kilometres event at the Finnish resort, after Therese Johaug led home Heidi Weng and Ingvild Flugstad Østberg in the women's 15km race.

Sundby's victory means the 31-year-old is closing in on a third consecutive World Cup title and came in a time of 1 hour 10:03 min.

The double Olympic medallist was 4.9 seconds ahead of Krogh with Holund coming home eight seconds adrift.

Norwegian skiers also claimed fourth and fifth place on a dominant day for the nation.

"I tried to create good speed in the first laps," said Sundby, who won with little drama at the finish despite a collision during the race.

"It was more difficult in the conditions we had today.

"I had a crash with a Russian skier.

"It took me a few laps to recover.

"The pace was quite fast from the beginning.

"I did not want to come with Finn in the last 100 metres.

"I gave everything with 1 km to go."

Therese Johaug was the women's champion over 15km
Therese Johaug was the women's champion over 15km ©Getty Images

Sundby now has 1960 points on top of the overall standings, with Krogh second but a long way back on 1256.

Petter Northug sits in third place on 1108 points.

In the women's race, Johaug became only the second woman to win 15 races in a season as the World Cup leader powered home in 38:59.9.

Only Marit Bjoergen has won more races in one season and she has done so twice, winning 17 times in 2011/12 and 15 times last season.

"I was a little bit nervous before the start because of snow conditions," said Johaug.

"I tried in the beginning to go away and I managed to create a gap.

"I had to fight hard to keep the distance on Heidi in the classic part.

"My skis were perfect.

"I love the track in Lahti."

Like Sundby, Johaug is dominating the overall women's table with a tally of 2025 points, with Østberg second on 1779.

Weng has 1557 in third ahead of the next World Cup event in Gatineau on March 1 - a sprint race which marks the start of the Ski Tour Canada.