Twitter has unsealed the documents for its planned initial public offering (IPO) of stock and says it hopes to raise up to $1bn (€738m).

Speculation is mounting that social networking giant Twitter may launch on the stock market as early as this August.

Current TV, the network co-founded by former US vice-president Al Gore, was sold for about $500m (€383m) to Al Jazeera, the Qatar-based news channel, according to two people with knowledge of the deal.

Billionaire money manager George Soros reported a nearly 2% stake in Manchester United Plc in one of the first revelations of investors in the British soccer club’s controversial initial public offering earlier this month.

Facebook is already trading like a public company as insiders and wealthy investors use private marketplaces to buy and sell stock in the social networking company, ahead of its initial offering.