Finland's Niskanen had won the 15 kilometres race three times before in Ruka and made it four with another impressive showing on home snow.

The two-time Olympic gold medallist completed the course in 33min 8.6sec, 8.3sec quicker than runner-up Alexey Chervotkin could manage.

Another Russian, Alexander Bolshunov, was third and five of the top eight were Russian.

Bolshunov was the overall winner of the last two FIS Cross-Country World Cups.

The women's 10km classic race was won by 22-year-old Swede Karlsson, who only had one previous World Cup victory to her name.

Karlsson was victorious in a rapid 24:09.4.

Three-time overall World Cup winner Therese Johaug from Norway was second, 13.7sec behind, and Germany's Katharina Hennig completed the top three.

Johaug is also the current world champion over this distance and the three world medallists from earlier this year all posted top-four finishes today.

Karlsson won a 10km silver medal at the Nordic Ski World Championships, while her compatriot Ebba Andersson - fourth today - was third in that race.

A women's 10km freestyle pursuit and men's 15km freestyle pursuit are due to be staged in Ruka tomorrow.