Jamie Vardy, Bilal El Khannouss and Patson Daka got the goals as Van Nistelrooy enjoyed a dream start to his new role shortly after his departure from Manchester United.

«On a long-term basis we know the performances need to get better. But the spirit and how we want to do things we saw today because, if not, the Premier League is too brutal,» said Van Nistelrooy.

The Dutchman said he had been «astonished» by the number of offers he received after a four-game spell as interim United boss, which included two wins over Leicester.

A lethal finisher in his playing days, Van Nistelrooy watched on approvingly as Vardy opened the scoring after just 99 seconds at the King Power.

The 37-year-old had initially been flagged offside, but a VAR review showed he was clearly on for his fifth goal of the season.

Defeat ramps up the scrutiny of Hammers boss Julen Lopetegui after a seventh defeat in 14 Premier League games.

The visitors enjoyed the majority of possession and had 31 shots to Leicester’s eight but failed to make it count.

A frustrating night because we deserved much more today,» said Lopetegui. «Normally we have to win this match but we didn’t because we didn’t score.»

West Ham did have a goal controversially ruled out when Leicester goalkeeper Mads Hermansen punched the ball into his own net and was relieved to be awarded a foul due to minimal contact from Tomas Soucek.

Conor Coady also cleared off the line from Crysencio Summerville in the second half.

But Leicester remained a threat on the counter-attack and doubled their lead when El Khannouss coolly stroked home Kasey McAteer’s pass.

Daka then blasted in to make it 3-0 before Niclas Fuellkrug netted a late consolation with his first West Ham goal.

Victory lifts Leicester up to 15th, four points above the relegation zone, and within two points of 14th-placed West Ham.