Striker Shinji Okazaki scored the only goal of the game with a stunning overhead kick -- the home side’s solitary shot on target -- to ruin newly-appointed Rafael Benitez’s first game in charge of the struggling Magpies.
Victory moved Leicester five points clear of second-placed Tottenham and 11 ahead of wilting Arsenal, although the Gunners and fourth-placed Manchester City both retain a game in hand.
The Foxes need a maximum of 20 points from their remaining eight matches to be crowned champions, while Ranieri remained steadfast in deflecting the notion that his side are on the cusp of one football’s greatest ever shocks.
“The race is open. We are fighting for Europe and then maybe with four of five matches left, maybe we are fighting for the Champions League,” said former Chelsea manager Ranieri. “I want to fight every match.
“Now our concentration is about Crystal Palace [on Saturday], another difficult match. We will go to battle there. We are so strong, we think only one match at a time. Step by step, that is our philosophy.”
Leicester were far from convincing but extended their unbeaten run to four matches, which includes three wins, while the clean sheet was also their third in that sequence.
“It wasn’t the best performance from us but we showed fantastic spirit,” added the Italian. “We defended very well. We fight.”
A sixth defeat in seven compounded struggling Newcastle’s relegation worries and they sit a point behind rivals Sunderland in 17th place ahead of Sunday’s Tyne-Wear derby at St James’ Park, although Benitez believes his side showcased survival credentials.
“There were a lot of positives and the team showed that they are convinced they can win,” said Benitez. “We did well, you could see the commitment and the passion. We cannot change this result but we can be happy in terms of the commitment of the players.”
Leicester had barely threatened during a scrappy opening but breached Newcastle’s defence in the 25th minute when spectacular improvisation gave former Mainz forward Okazaki his first goal at the King Power Stadium.
The 29-year-old produced a dazzling overhead kick to divert Jamie Vardy’s header across goal, following Marc Albrighton’s ball into the penalty area, beyond Newcastle goalkeeper Rob Elliot.
The Foxes were close to doubling their lead before the half-hour mark when Albrighton stormed onto a loose ball, only for his low curling shot to evade Elliot’s post.
Newcastle have only scored seven away league goals this season and failed to overly trouble Leicester goalkeeper Kasper Schmeichel during the second half despite periods of possession and a sense of anxiousness in the home side’s ranks.