The unbeaten Ospreys pushed the North all the way at Llandarcy Academy in a game between the top two. However, penalties from outside half Joseph Griffin and fullback Harley Thompson earned the North a second successive victory of the season.
Tom Prydie kicked a first half penalty for the Ospreys, but it was not enough to deny the North a 6-3 victory which, come the end of the season, could prove significant.
At the Memorial Ground in Ely, the South made light work of the Dragons, winning 24-5, albeit without a bonus point.
Fullback Elliot Jones, lock Dan Crimmins and wing Ioan Mortimer crossed for tries with Dave Lakin adding two conversions and a penalty and replacement Diggy Bird a further conversion.
For the Dragons, who have yet to register a victory in the competition, Dafydd Carter bagged a consolation try.
Blues High Performance Manager Gafyn Cooper said, “It was another good night for the region and we are obviously delighted with the two results.
“The Dragons are always a difficult side to beat, especially as they seem to be turning out some big, powerful packs this season. However, we stood up to that and came away with the points.
“The North’s result is even more impressive. The Ospreys rarely lose on home soil, so to go down there and restrict then to a single penalty tells you something about the spirit and desire that exists within that team.”
Ospreys: T Prydie; B Barlow, D Howell, K Blackmore, E Walker; O Williams, R Jones (Capt); R Apsee, R Curties, J Fraser, S Davies, B Davies, R Kehoe, M Sully, D Baker
Replacements: T Habberfield, M Morgan, S Hughes, S Pick, M Carpenter, L Evans, D Saines
Blues South: E Jones; I Mortimer, N Gumbleton, A Cooke, A Williams; D Lakin, J Lewis; M Savery, J Deabrau, L Davies, D Crimmins, T Connolly, J Wilson, R Fenton (Capt), G Jones
Replacements: R Davies, A O’Malia, J Gape, R Tucker, S Curtis, D Bird, D Evans
Blues North: H Thompson; A Webber, O Williams, S Campbell (Capt), B Jones; J Griffin, K Marmion; T Emanuel, C Williams, O Davies, M Cook, J Barley, O Sheppard, T Young, D Barry
Replacements: L Smout, J Williams, J Gibbon, D Waldin, J Wills, L Williams, E Sherlock
Dragons: S Bevan; L Foley, A Cooper, M Channing, M Jolly; L Roblin, J Evans; L Bacon, L Jones, A Yule, R Griffiths, A Hughes, G Rogers, G Evans, R Wilson (Capt)
Replacements: R Paul, T Rusgas, C Penna, A Herbert, D Carter, L Ford, G Kemp