Red and White Holdings - an Alisher Usmanov-owned company chaired by David Dein - has increased its share in Arsenal to over 25%.
By upping his stake in the Premier League club the Russian billionaire, who held a 24.9% stake in the club without having a seat on the board, is sure to spark fresh speculation that he is gathering funds to reach the 29.9% needed to force a mandatory takeover offer.
In a statement, the company said the increase in their shareholding was "in line with Red and White's previously stated intention to secure a significant shareholding in Arsenal and ensure that its position is protected".
The statement added: "We are pleased to have now secured over a quarter of the shares of Arsenal. We are committed long-term investors and supporters of the club and are comfortable that we are now in a protected position.
"We also welcome the strengthening of the squad and look forward to a successful conclusion to the season."
Earlier this month the club's new chief executive, Ivan Gazidis, told the Guardian that he planned to meet with the Russian oligarch (who has an estimated fortune of $4.5bn) to discuss his intentions.
"He is a significant shareholder and somebody all of us in the board, including me, will want to meet with, understand better and get to know better," said Gazidis.
Arsenal have long had a reputation as a 'family-run' club, but have had to deal with upheavals in recent years; director Lady Nina Bracewell-Smith was forced out in December of last year and David Dein, who sold his shares to Usmanov, left the board in 2007 amid disagreement's over the club's future funding.
Arsenal's board of directors have remained steadfast in their determination not to sell out for some time and had entered into a "lockdown" agreement whereby no director could sell their holding before April and thereafter must give each other first option.
However, the situation changed in December when Bracewell-Smith was forced off the board meaning her 15.9% holding was consequently freed from the terms of the agreement.
American Stan Kroenke, the owner of the Colorado Rapids MLS soccer franchise, also has a 12.4% holding, but he has aligned himself with the Arsenal directors having accepted a seat on the board.
The other major shareholder is Daniel Fiszman, who owns a 24.11% stake.
Red & White was formed in August 2007 following the initial sale of former vice-chairman Dein's 14.65% stake in the north London club. By October 2008 they had increased their stake to 23% and that became just over 24% almost a year to the day before Monday's increase.