Fallen Scottish giants Rangers plan to raise an extra £4 million ($6.6 million, 5 million euros) via an open share offer to existing shareholders, the Glasgow giants announced Friday.

The London Stock Exchange was told the Ibrox club hope the latest cash injection will help "re-build and re-establish Rangers as a stable, sustainable and successful business".

Rangers also said they expected to raise "between £20 million and £30 million" over the next three years with the open offer an "important planned part of this fund raising strategy."

However, officials warned Rangers faced an "uncertain future" if subscriptions to the offer fell below a minimum level.

Graham Wallace, the Rangers chief executive said in April the club may have to turn to existing shareholders in a bid to make up revenue after it was revealed they had got through nearly £70m in the 18 months since it was reformed following liquidation.

Rangers will offer 19,864,918 new Ordinary Shares at 20p each and the open offer is not underwritten.

If the aggregate level of subscription is less than 15,000,000 the open offer will not proceed.

In that event, "the company will be unable to pay its creditors as they fall due and the future of the Company will be uncertain; The Directors will immediately have to seek emergency financing which may or may not be available," Rangers said.

Some fans have vented their anger at what they see as the board's mismanagement by refusing to buy tickets, with season ticket sales having dropped to "approximately" 23,000 from around 38,000 last year, even though Rangers have been promoted to the second-tier Championship.

Rangers, the 54-times champions of Scotland, were kicked into the country's fourth and bottom tier of professional football in 2012 after entering administration. But they have since been working their way back towards the summit and last season were crowned champions of third-tier League One.