THREE goals in the space of nine minutes either side of half-time enabled Barnsley to end a tough week in scintillating fashion as Leeds United's six-match unbeaten league sequence was ended on a riproaring night at Oakwell - which was marred by pockets of crowd trouble.
Despite taking the lead on 18 minutes from top-scorer Chris Wood, Leeds were forced to ensure a fraught night in the main against vibrant hosts who produced a high-tempo performance which was rewarded by three excellent goals.
A well-placed Tom Bradshaw header drew the Reds level just before the break, before a clinical strike from Ryan Kent put them ahead on 48 minutes.
A wonderful free-kick from Conor Hourihane soon provided the hosts wth a two-goal advantage and despite Wood pulling one back from the spot after referee Mike Dean blotted his copybook by erroneously awarding a penalty when Marc Roberts' handball offence was outside the box, Barnsley held on for a famous win.
A spicy first half ensued with the sight of Hourihane lining up from the start for the hosts being a welcome sight for Reds supporters.
It was a half in which the hosts started and finished well, with Leeds, after a tentative start, possessed the more poise in between and displayed a real threat, particularly at set-pieces with the visitors winning seven corners.
The deliveries of Pablo Hernandez proved a danger all half and it was from one which led to the breakthrough when Wood took advantage of slack marking to bundle home.
The goal was the prelude to some unsavoury crowd scenes with both sets of supporters clashing in the corner of the Executive Stand and then briefly on the left-hand side of the Pontefract Road end before order was eventually restored.
Sentinel-like defending on the line from debutant Gethin Jones then saved the day to clear Wood's header before Souleymane Doukara's snapshot was beaten away by Adam Davies as Leeds scented a second.
Barnsley eventually regrouped and posed threat from set-pieces too and Angus MacDonald should have done better with a free header from Ryan Kent's free-kick, but his header was straight at Rob Green before Marc Roberts nodded over when well placed from another Kent delivery.
But parity was restored with smart movement by Bradshaw saw him evade the Leeds backline with his neat header from Adam Armstrong's cross flying past Green, while MacDonald inches wide with another header seconds before the interval following Hourihane's inswinging corner.
Barnsley continued with a vibrant tempo on the restart and manufactured a clinical second goal, ,aided by some dodgy Leeds' defending.
Watkins cross found its way to Kent, who was afforded time much time and space, although his turn and precision low shot was top-class.
It got worse for Leeds, with a magical moment from Hourihane providing the hosts with a two-goal cushion, with his exquisite free-kick flying past the bemused Green after Roofe was penalised for a foul on Scowen.
It was turning into a fraught night for United, but they were afforded a lifeline thanks to a poor decision from Dean who penalised Roberts for a handball offence outside of the box.
Leeds pushed forward for a leveller late on, with Roofe missing a chance and sub Stuart Dallas a whisker away, but Barnsley deservedly took the derby spoils and points.