City slipped to their first defeat in five games as Luciano Becchio’s early penalty earned dogged Leeds a hard-fought victory at Elland Road.
United’s Argentine striker gave Neil Warnock’s men the lead after just three minutes following Jeff Schlupp’s trip youngster Sam Byram.
And it was an advantage the Yorkshire side clung desperately to, as Nigel Pearson’s Foxes threw everything at them to preserve their recent unbeaten run.
Better in the second half after a frustrating first period, the Foxes still struggled to produce the slick passing football that inspired their recent wins over Ipswich Town and Sheffield Wednesday, as Leeds set about disrupting their rhythm with a tireless pressing game.
And while Martyn Waghorn and substitute Marko Futacs both threatened to level the scores, Pearson's men were left to reflect on a defeat that sees them drop to fourth in the table ahead of an East Midlands clash with Derby at King Power Stadium on Saturday.
Coming off the back of respective weekend wins, both managers fielded unchanged sides at Elland Road, as Leeds looked to build on their first win in eight and City went in search of a third in succession.
A moment of applause for the late Gary Speed, a Leeds United legend who passed away a year ago to the day, preceded kick-off. The Leeds fans rarely need an excuse to get going, but it certainly added a couple of decibels to the noise levels.
Their side made the perfect start, striking with their first attack as the highly-rated Byram made his first advance into Leicester territory. Seizing on a knockdown from Becchio, the young full-back lured Schlupp into a mistimed challenge in the right side of the box.
Referee Mick Russell pointed to the spot and Becchio hammered home his 12th goal of the season.
It was by no means the start Kasper Schmeichel would have wanted. Like Lee Peltier, playing on the left of the Leeds back four, the Dane looked a man in determined mood against former employers.
It was down Peltier’s left that City’s early problems were coming, as West Bromwich Albion loanee Jerome Thomas gave Ritchie De Laet a thorough first-half examination.
But De Laet gave as good as he got, charging forward on the counter-attack from Jamie Vardy’s pass on 13 minutes to draw a watchful save from Paddy Kenny.
An intriguing battle was raging down that flank, a duel Becchio joined on 27 minutes to produce an inviting cross for the arriving Paul Green. The diminutive winger controlled his first-time shot perfectly, but was denied by the athleticism of Schmeichel.
The home side’s hard pressing game was serving them well, with the influential Danny Drinkwater coming in for particular harassment from terriers in white. Even the enigmatic El-Hadji Diouf was chasing blue shirts.
But the Foxes kept their heads and produced moments of encouragement before the break – not least when Tom Lees could only partly clear Ben Marshall’s cross from the left, tempting Martyn Waghorn into a venomous volley that shaved the face of the crossbar from a tight angle.
And a better chance would materialise for Vardy a minute before half-time, but the hard-working striker could not hit the target with his volley after Lees had blocked a shot from Andy King.
The second half started with City on the front foot, but Waghorn was crowded out inside the box after appearing to be clear from Vardy’s well-weighted pass.
And when Waghorn’s whipped free-kick from the right found the unmarked head of Wes Morgan, Kenny was well-positioned to make a routine save.
Pearson moved boldly, introducing Anthony Knockaert and Marko Futacs to the action and the latter’s quality was immediately evident as he headed down for Waghorn to drive over from distance.
The visitors were beginning to pin their hosts back, prompting Warnock to replace the flair of Thomas with the tenacity of Michael Brown.
And one wonders whether Thomas might have made a better job of Becchio’s neat lay-off on 65 minutes, which Brown could only curl wide with the whole goal to aim at.
But what Brown did bring to the Leeds side was added steel in the middle of the park – a valuable ingredient as the hosts sought to slow the pace of the game through any means necessary.
City continued to threaten, but with less regularity. Drinkwater hung a cross deep into the Leeds box with 13 minutes to go, Alan Tate could only flick the ball behind him a Futacs flashed a fierce half-volley a foot wide of the far post.
Leeds’ determination swelled and the home fans united behind them, greeting every decision with deafening approval.
And despite City tossing a flurry of late balls into the Leeds box in the game’s closing stages, they were unable to fashion the genuine chance that might have rescued a point.
Leeds (4-4-2): Kenny; Byram, Lees, Tate, Peltier (c); Green, Tonge, Norris, Thomas (Brown 61); Diouf, Becchio.
Unused subs: Ashdown, Drury, White, Gray, Hall, McCormack.
Goals: Becchio 3 pen
City (4-4-2): Schmeichel; De Laet, Morgan (c), Whitbread, Schlupp; Marshall (Knockaert 57), Drinkwater, King, Dyer; Vardy (Futacs 57), Waghorn (Lingard 77).
Unused subs: Logan, Konchesky, James, Moore.
Booked: De Laet
Referee: Mick Russell (Hertfordshire)