Ayoze Perez's late own goal cost Newcastle a precious Premier League draw as Leicester ruined the Magpies' 125th birthday celebrations.
Substitute Perez thumped the ball into his own net four minutes from time in his efforts to prevent Shinji Okazaki from converting Jamie Vardy's cross, just as it looked as though Dwight Gayle's equaliser had clinched just a second Premier League point in seven games.
In the process, he handed Leicester, who had bounced back from Joselu's early opener with goals from Riyad Mahrez and Demarai Gray, a third successive league win in front of a crowd of 52,117 at St James' Park.
The majority of them left already fearing the worst if the reinforcements manager Rafael Benitez wants do not arrive in January, regardless of whether or not a takeover is completed, after seeing Huddersfield, Swansea and West Ham all win earlier in the day to leave their club just two points clear of the relegation zone.
Newcastle needed to start positively, and they did just that as Jacob Murphy picked out Gayle down the left and he pulled back for Joselu to thump in his first goal since October 1 with only five minutes played.
It might have been even better two minutes later when Gayle found himself in space, but saw his left-foot strike fly just wide of a relieved Kasper Schmeichel's far post.
However, Leicester responded well and Gray forced Karl Darlow into an uncomfortable ninth-minute save at his near post and then curled a shot inches wide after slipping past Mikel Merino four minutes later.
The visitors were level with 20 minutes gone when, after Merino had squandered possession on halfway, Mahrez was allowed to advance towards goal before unleashing a thunderbolt of a drive which flew into the net, despite Darlow getting his fingertips to it.
The Foxes threatened repeatedly on the counter and Darlow was relieved to see an offside flag raised after he could only parry Marc Albrighton's effort, while full-back DeAndre Yedlin intervened in the nick of time to deny Vardy a 28th-minute goal.
Newcastle attacked sporadically and Murphy called upon Schmeichel to make a diving save nine minutes before the break, but it was City who headed for the dressing room the more satisfied.
The home side's negligence on the ball continued to cost them as the second half unfolded, and Leicester went ahead for the first time on the hour when Albrighton's fine first-time lay-off from Mahrez's raking pass allowed Gray to control and fire past Darlow with the help of a deflection off defender Florian Lejeune.
Darlow had to claw away Mahrez's driven 66th-minute cross as the Foxes went for the kill, but his side were level with 17 minutes remaining when, amid a goalmouth scramble, Gayle found time to control and dispatch a shot which flew past Schmeichel off Harry Maguire's out-stretched leg.
But the Magpies were caught on the break at the death when Perez could only turn the ball into his own net as he tried to desperately to get to fellow substitute Okazaki.