Ex-Newport Gwent Dragons prop Ian George crashed over twice to bag a bonus point win at Eugene Cross Park.
The Steelmen were the only side in the top four to win and jumped a point ahead of Neath who were held 18-18 at the Gnoll by Llanelli. Ospreys flanker Lee Beach scored for the All Blacks but Isan Evans and Matthew Jacob replied for Llanelli.
Cardiff remain third despite crashing 42-14 at Aberavon who crossed five times. Lloyd Howells got the rout under way with the opener.
Nicky Thomas kicked the winner for Swansea in a nail-biting 10-8 triumph against Pontypridd who slip two places to eighth in the table.
Cross Keys move above Ponty after beating Glamorgan Wanderers 13-8 while Bedwas fullback Jason Tovey scored 15 points, including one try, in their 25-7 win at Llandovery.
Newport edged a vital 16-12 win against Bridgend at Rodney Parade that saw five players shown yellow cards. Daniel Connolly and Ioan Cunningham both crossed for Bridgend who took a bonus point.
