Klemettinen prevailed in the opening women's heat having finished the course in a time of 23min 31sec, with team-mate Anu Tuomisto second and Germany's Dorothea Mueller third.

Ojanaho had earlier triumphed in the first men's qualifier, outclassing the rest of the field by clocking 21:18.

His time was over two minutes faster than nearest challenger Henrik Johansson, while Norway's Elias Jonsson came through in third.

Akseli Ruohola completed the Finnish success on the opening day of the event, jointly winning the third men's heat in 23:04 with Frenchman Mathieu Perrin.

Joey Hadorn of Switzerland was third.

The other men's heat was won by Simon Imark as he led home a Swedish one-two in front of Simon Hector in a time of 24:01.

Switzerland earned two victories in the women's heats as Simona Aebersold triumphed in the second race in 23:32.

Linnea Golsater of Sweden was second and Norwegian Ingrid Lundanes finished third.

Sofie Bachmann beat Swiss team-mate Valerie Aebischer in the third and final heat by stopping the clock at 24:43.

Danish competitor Agnes Kracht did enough for third.

The top 20 in each of the three men's and women's heats secured a place in tomorrow's final, where the junior world champions will be crowned.