Marcelo Bielsa's side has been inconsistent since last month's restart but saw off Blackburn to remain six points clear of third-placed Brentford.
West Bromwich Albion, which sits in second, is not in action until Monday (AEST) and in-form Brentford took full advantage by closing the gap to two points with a convincing 3-0 win against Wigan Athletic.
Stoke City was also a big winner in Sunday's (AEST) second-tier fixtures, thrashing fellow struggler Barnsley 4-0 to climb out of the relegation zone and into 18th place.
Cardiff City, Reading and Fulham picked up valuable victories of their own, while two other matches — including the east Midlands derby — finished level.
TOP-FLIGHT RETURN IN SIGHT FOR LEEDS
Leeds had collected four points from nine since resuming its campaign, but there is surely no stopping it from ending its 16-year wait for top-flight promotion after this win.
Patrick Bamford and Kalvin Phillips put Leeds two goals ahead and while Adam Armstrong scored a free-kick early in the second period, Mateusz Klich made sure of the points.
West Brom plays its game in hand against Hull City on Monday (AEST) and now has a four-point gap to make up on Leeds, although holding down second place could become its main priority.
Brentford has now won five in a row after Said Benrahma helped himself to a hat-trick against Wigan, which had Joe Garner sent off late on.
PROMOTION BATTLE HEATING UP
Derby County and Nottingham Forest played out a 1-1 draw in the early kick-off, Chris Martin scoring in the 97th minute to cancel out Joe Lolley's goal.
Cardiff saw a number of promising chances go begging against Bristol City before Lee Tomlin played in fellow substitute Danny Ward to snatch a 1-0 win.
As well as earning bragging rights for Cardiff, Ward's clinical strike five minutes from the end also opens up a three-point buffer on seventh-in-the-table Derby.
Fulham also needed a late goal to overcome Birmingham City at Craven Cottage, Josh Onomah popping up deep into added time to prolong the visitors' bad run of form.
STOKE STEERS CLEAR OF DANGER
Stoke entered its match with Barnsley sitting just above its opponent in the relegation zone. By the final whistle, the Potters had risen clear of the drop zone.
Tyrese Campbell struck twice while a goal apiece for Sam Vokes and Tom Ince resulted in a crushing win at bet365 Stadium.
Luton Town was unable to give its own survival hopes a much-needed boost as it went down 5-0 at home to Reading, a result that leaves it five points from safety.
Yakou Meite was the hero for Reading, netting four of its goals, including an 18-minute hat-trick before half-time, while George Puscas was also on target for the visitors.
Meanwhile, Huddersfield Town played out a goalless stalemate with a Preston North End side now winless in six matches.