BEIJING/SHANGHAI (Reuters) - Beijing intensified efforts at the weekend to pull China's stock markets out of a nose-dive that is threatening the world's second-largest economy, with top brokerages pledging to buy massive amounts of shares and a report that the government has set up a market stabilization fund.
Beijing has also suspended new share offers in an attempt to take pressure off the market after a 30 percent plunge in three weeks, the Wall Street Journal said.
The reported suspension of initial public offers (IPOs) came a few hours after extraordinary announcements by major brokers and fund managers, which collectively pledged to invest at least $19 billion of their own money into stocks.
China's government, regulators and financial institutions are now waging a concerted campaign to prop up the nation's stock markets, amid fears that a meltdown would rock the financial system and inflict heavy losses across an economy where annual growth is already running at a 24-year low.
Almost $3 trillion in market value - more than the entire economic output of Brazil - has been wiped out since markets went into reverse just a few weeks ago, posing a bigger headache for many global investors than even the Greek debt crisis.
The main Shanghai Composite Index has lost nearly a third of its value since mid-June, a dramatic end to an equally breathtaking rally that saw it more than double in just seven months, fueled by official interest-rate cuts.
The sell-off is especially worrying because the bull market had been built on a mountain of speculative loans. Some analysts suggest total margin lending, both formal and informal, could add up to around 4 trillion yuan ($645 billion).
China's stock markets are dominated by retail investors, and a full-blown collapse could fuel fears of panic. State TV said on Sunday police had detained a man who allegedly spread rumors about people jumping off buildings after the share crash.
Repeated attempts by regulators over the last week to stabilize markets -- including an interest rate cut, a relaxation of margin-lending rules and additional bank liquidity -- have failed to reassure panicky investors so far.
But Samuel Chien, a partner of Shanghai-based hedge fund BoomTrend Investment Management Co, said that he's ready to pile into blue-chip stocks this week, betting the more aggressive weekend measures would trigger a rebound.
Brokerages have promised not to sell their new holdings as long as the Shanghai Composite Index is below 4,500 points, well above current levels of 3,684, Chien noted. That new buying, if it occurs, should blunt selling pressure.
"Main indexes will rise. I have ample cash at hand, and surely will buy."
But he said there are still huge risks in investing in far more speculative small stocks. "In the small cap sphere, it's still very chaotic. Some stocks are still over-valued and continue to face huge pressure."
Saturday's pledge by China's top brokerages to collectively buy at least 120 billion yuan ($19.3 billion) of shares would form part of Beijing's new market stabilization fund, according to the Wall Street Journal.
Separately on Saturday, 25 Chinese mutual funds announced they, too, would put their own capital into stocks. The fund managers did not give a figure but said they would invest in their own funds, alongside their customers.
Later in the day, 28 Chinese firms announced in individual statements they would suspend their own IPO plans. They did not mention any central decision to halt IPOs.
The securities regulator had already said on Friday it would reduce the number of IPOs and other capital-raisings.
The freezing of IPOs can lend support to a falling market because large amounts of money are frozen when subscriptions are taken, drying up liquidity in the market and threatening to push up interest rates, adding to companies' financing costs.
Large IPOs have been cited as a reason for triggering the plunge, though only recently Beijing seemed intent on letting more sales proceed, perhaps in hopes that greater supply in the market would temper the sizzling rally without snuffing it out.
In its statement, the Securities Association of China said top brokerages would jointly invest 15 percent of their net assets as of end-June, "or no less than 120 billion yuan", in blue-chip exchange traded funds.
Listed securities companies among the 21 brokerages also pledged to buy back shares, along with their major shareholders.
The Asset Management Association of China promised to hold their additional stock investments for at least a year.
Just a few months ago, state media had been encouraging the market's giddy rise, saying China's bull market had just begun and denying that it was in a bubble. Investors big and small took that as a government signal to pile in.
Now, Beijing is struggling to restore confidence before too much economic damage is done.
Weighed down by a property downturn, factory overcapacity and high levels of local government debt, economic growth had already been expected to slow to around 7 percent in 2015, robust by global standards but its weakest annual expansion in a quarter of a century.
($1 = 6.2047 Chinese yuan)
Editing by Kazunori Takada, Mark Bendeich & Kim Coghill