• Ineos owner Sir Jim Ratcliffe put in his second bid to buy the club after Wednesday's confusion and extended deadline.
• Ratcliffe and Qatari banker Sheikh Jassim were the only publicly declared bidders until Zilliacus announced his offer.
Finnish entrepreneur Thomas Zilliacus says he has submitted a bid to buy Manchester United.
Zilliacus wants to buy half of the club with the other half bought by fans, who will be part of club decision-making.
Later on Thursday, Ineos owner Sir Jim Ratcliffe put in his second bid to buy the club after Wednesday's confusion and extended deadline.
Interested parties had until 21:00 GMT on Wednesday to enter their bids before the deadline was extended.
On Thursday, an Ineos spokesperson said "Ratcliffe and Ineos can confirm we have submitted a revised bid".
Ratcliffe and Qatari banker Sheikh Jassim were the only publicly declared bidders until Zilliacus announced his offer.
As yet there has been no confirmation from Sheikh Jassim but he is expected to submit a second bid.
Zilliacus said: "Any sport club ultimately should belong to its fans. My bid is built on equality with fans.
"The current development, where billionaire sheiks and oligarchs take over clubs and control them as their personal playgrounds is not a healthy trend.
"The current market value of the club is just under $3.9bn (£3.17bn). That means that if every one of the fans of the club would join in buying the club, the total sum per fan would amount to less than $6.
"My group will finance half of the sum needed to take over the club, and will ask the fans, through a new company that is being set up for this specific purpose, to participate for the other half.
"If every fan joins it means less than $3 per fan."
Zilliacus plans to give fans a say through an app from which they can "participate and cast" their vote "when deciding on footballing matters relating to the club".
It is also understood US investment company Elliott has made an offer to purchase a minority stake, irrespective of who ends up owning the club.
Zilliacus, who has previously been involved with HJK Helsinki and ice hockey champions Jokerit in his homeland, is the founder and chairman of new social media group novaM Group.
He wants to buy United through XXI Century Capital, which is an investment firm owned by his holding company.