Cross Keys caused a major shock by securing an unlikely 25-20 triumph at Principality Premierhsip leaders Llanelli.
A penalty try for the visitors was sandwiched between strikes from Owen Jones and Will Johnstone's second-half winner to influct Llanelli's third league defeat of the season.
Llanelli rallied through scores from Mike Davies and number eight Dan Godfrey and the result leaves the hosts one point clear at the top of the Princiaplaity Premiership.
The hosts looked to be cruising with a 17-10 half-time lead at Parc y Scarlets with Dan Evans adding two conversions and a penalty. But Cross Keys went ahead through the penalty try and Johnstone's 52nd minute try.
Evans added a penalty to reduce the lead to 22-20 but opposite number Joe Deakin, who had already hammered home two conversions and a penalty, calmly slotted home a 58th penalty to ease the tension and seal an unexpected win.
Meanwhile. Aberavon cruised to a bonus-point win against Bedwas at the Talbot Athletic Ground.
The Wizards kept their winning run going, after a 74-0 hammering of Division Three club Llantwit Fardre 74-0 in the SWALEC Cup last weekend, and recorded the four tries early in the game.
But they trailed the Premiership strugglers just minutes into the game, but took control early in the second half, scoring tries through flanker Chris Davies and winger Richard Carter within the first ten minutes after the restart.
Bedwas had no response and the kicking of outside-half Jamie Davies saw the game end 38-10 in Aberavon's favour.
Cardiff came from behind to beat Ebbw Vale 15-13 thanks to the contribution of a pair of replacements.
The Blue-Blacks had made nine changes from the XV that lost at Llanelli last week yet it was prop Richard Cornock, who didn't figure at Parc y Scarlets, who came off the bench to help Cardiff secure a win, as late on he pushed over to level the scoreline.
Another replacement, outside-half Gareth Davies, slotted over the conversion to hand the Blue-Blacks four points.
Newport claimed a stunning 34-32 victory over defending champions Neath in a thriller at Rodney Parade.
Tom Riley scored in either half and was ably supported by strikes from Mike Poole and Andrew Coombs in a match which saw the lead change hands nine times.
Neath hit back through tries from Luke Ford and David Lockyer to ensure a losing bonus point for the Welsh All Blacks.
Wales full-back Kevin Morgan started for Newport as the 48-cap star continues his recovery from a serious Achilles tendon injury.
And his influence spread to his fellow backs as early as the second minute when Riley crossed for the opening try.
Newport held a slender 17-16 advantage at the break and were pinned back by the goalkicking of Arwel Thomas who claimed a 22-point tally including six penalties and two conversions.
But Newport replacement kicker Dan Griffiths booted four penalties to get the hosts over the finishing line.
Leigh Bevan was the hero for mid-table Swansea who recorded a comprehensive 39-3 bonus-point victory over struggling Bridgend.
Wing wizard Bevan opened and finished the scoring in a convincing five-try triumph at St Helens.
The hosts were able to include Ospreys' scrum-half Rhodri Wells and his quick distribution allowed his fellow backs to produce free flowing running rugby.
Full-back Nicky Thomas grabbed the second try before adding four conversions and two penalties in an impressive 19-point haul.
Bridgend finally got themselves on the scoreboard when fly-half Gareth David's penalty grabbed their only points on a disappointing afternoon for the visitors.
But Swansea back-rower Sam Kiley added a third for the Whites to put Richard Webster men's into a commanding 22-3 interval lead.
Centre David Watts grabbed the bonus-point for the home side early in the second period before Bevan sealed victory with his second score.
There was a tie on Saturday at Glamorgan Wanderers and Pontypridd both scored 13.
Scott Sneddon scored a penalty with the last kick of the game to seal a stunning second-half comeback from the Wanderers.
The result leaves both sides safe in mid-table with little prospect of any end-of-season nerves at either end of the table.
Pontypool emerged narrow 10-6 victors over Llandovery in the Welsh Premiership basement battle.
Tries in either half from Sam Mills and Gareth Williams handed the bottom side only their fourth win of the season at Church Bank and leave them five points adrift of their nearest rivals.
Sam Cross and Luke Treharne have been named as co-captains of the Wales Sevens side as head coach Gareth Williams names his 12-man squad to play in the first leg of the HSBC World Series in Dubai next weekend.
Bedwas head coach Steve Law and players Nicky Griffiths and Alun Rees extol the virtues of the close knit club as they prepare to host third place RGC 1404 - who are one place head of them on the Principality Premiership points table - on Saturday.
Many of the Wales squad have said Diolch (thank you) to someone who played an important part in their early playing days by nominating them to be invited to the Wales v South Africa match. One person, Gowerton Comprehensive geography teacher Mr Dean Mason was nominated by two of his former pupils, Dan Biggar and Sam Davies.
The second WRU disability rugby pilot has been delivered, this time in Caerphilly schools, culminating in a festival at the Caerphilly Centre of Sporting Excellence, Ystrad Mynach tomorrow. Plans are in place to set up a Disability Rugby Club in Newbridge to provide long-term playing opportunities.
WRU TV: Hear from inside the Wales camp as Neil Jenkins discusses this weekend's clash with South Africa and how the squad are looking to put in a strong performance to round of the 2016 Under Armour Series