West Ham co-chairmen David Sullivan and David Gold have complained of being targeted for abuse by Leicester supporters in Sunday's draw at the Walkers Stadium.
The 2-2 result came as a blow to Leicester's Barclays Premier League title ambitions, with only a late penalty from Leonardo Ulloa sparing the Foxes from defeat.
Leicester led through Jamie Vardy's goal, but the striker was later sent off and Andy Carroll's penalty drew the teams level before Aaron Cresswell fired West Ham ahead. Carroll's challenge on Jeff Schlupp was punished with the stoppage-time penalty from which Leicester forced the draw.
Sullivan told the Daily Mirror: "We didn't stay to applaud our own players off as we felt threatened. We've spoken to Leicester and they've told us they would look into it."
Gold wrote on Twitter: "Elderly Leicester fans turned into monsters when WHU went 2-1 up then returned to nice old people when LCFC equalised."
He added on Tuesday: "I want Leicester to win the PL and I am pleased for their fans but their behaviour towards us was unacceptable."
Slaven Bilic admits Leicester's "fairytale" season has put West Ham's success in the shade.
The Hammers are still fighting for a top-four finish and a place in the Champions League with six games remaining.
But on Sunday they head to the King Power Stadium to take on a Foxes side on the verge of an incredible Premier League title, just a year after looking like certainties for relegation.
"People recognise we are having a good season, we are playing good football, and they are praising us," said Hammers boss Bilic.
"But what Leicester have done puts our successful season a little bit in the shadows.
"That's normal. It's like a fairytale and they deserve all the credit they are getting. It is unbelievable."
Marcus Rashford and Marouane Fellaini fired Man United to Wembley as West Ham's last ever FA Cup tie at Upton Park ended in defeatRead the full story ›
Get all the latest football gossip as Theo Walcott could move across LondonRead the full story ›
West Ham boss Slaven Bilic believes Andy Carroll's hat-trick heroics against Arsenal have catapulted him back into the England reckoning.
Striker Carroll plundered a stunning treble in just eight minutes either side of half-time in a thrilling 3-3 draw at Upton Park.
The 27-year-old was involved in Roy Hodgson's squad at the last European Championships in Poland and Ukraine in 2012 and opened the scoring in the victory over Sweden in the group stage.
Carroll has struggled with injuries since, but Bilic feels that if he can stay fit his aerial prowess would be a major asset for Hodgson and the Three Lions in France this summer.
"I've said my opinion about a few of our players." said Bilic.
"Mark Noble, Aaron Cresswell, and Andy Carroll is definitely in the category that he has to make you think about him because there are not many players capable of doing what he is doing. But it's Roy's decision.
"His problem is not consistency in terms of little injuries. A lad who is six foot whatever and with so many kilos - he needs to be fit. Now he is fit we hope he is going to last like this for years."
West Ham have increased the match day capacity at the former Olympic Stadium to 60,000 in response to spectator demand.
The Hammers are due to leave Upton Park at the end of this season and will play at the stadium in Stratford from the start of the 2016-17 season.
The original capacity was set to be 54,000 but after the number of people registered on the Hammers season ticket priority list exceeded the number of seats originally available at the multi-use stadium, that has been increased by 6,000.
"Today's announcement is further evidence of the upward trajectory of this club," said West Ham vice-chairman Karren Brady in a statement on the Hammers website.
"We are on course for what could be our most successful Premier League performance ever and our ambitions to finish in the top six and break into Europe are very much within reach.
"West Ham fans are famous the world over for their wonderful support. They have demonstrated this once again at matches this season and in the way that they have embraced the move to the new ground. We are delighted to be able to reward that magnificent support by releasing additional season tickets and bring even more visitors to the Park to enjoy all that it has to offer.
"The 2016-17 season looks bright for the team, the club and our fans. Not only will we have one of the world's greatest new stadiums, but now it will be one of the very largest in the world's most-watched league - a stadium with both the quality and the capacity to match our ambitions."
West Ham boss Slaven Bilic insists a top-four finish in the Barclays Premier League is now a realistic ambition.
A 1-0 victory over Tottenham on Wednesday has left the sixth-placed Hammers just one point adrift of the Champions League spots with Saturday's visit to Everton the first of their remaining 10 matches this season.
Bilic admits the club's position in the table justifies talk of claiming a coveted berth in the top four, but is also cautious over setting his sights too high.
"It is realistic now. We are one point behind with 10 games to go so we have a chance," Bilic said.
"But it's so tight and there are still a lot of games to go. Of course we are looking above us because we are very close to those places.
"We are also looking below us because there are teams who are queuing up. The gap is not big between us and ninth or 10th in the table."
Spurs couldn't capatalize on the opportunity to go top of the Premier League as they lost at West HamRead the full story ›
Injury-jinxed West Ham striker Andy Carroll is back on the treatment table and will miss Sunday's FA Cup clash at Blackburn.
The 27-year-old forward had just returned from a month out with a hamstring problem when he suffered an adductor injury after coming on as a substitute during last weekend's 2-2 draw at Norwich.
Carroll has been beset by injury problems since joining the Hammers and has started just 31 Premier League games in two-and-a-half years.
But co-chairman David Gold hopes the latest setback will not mean another lengthy lay-off for their £15million club-record signing.
Gold wrote on Twitter: "Andy has a slight injury and will be rested for the game against Blackburn."
West Ham's injuries are piling up ahead of Saturday's Premier League trip to NorwichRead the full story ›