Asian stocks fell on Wednesday as investors feared fresh rate cuts in China would not be enough stabilise its cooling economy or halt a collapse in its stock markets.

China's key share indexes attempted to move higher several times in early trade only to be slapped back by waves of selling, reflecting investors' views that much more support was needed from the government and the central bank.

Following a near 20 per cent plunge in stock prices in three days, the People's Bank of China cut interest rates late on Tuesday and lowered the amount of reserves that banks must hold in a much-anticipated move that some economists said was long overdue.

While the double-barrelled policy moves were initially cheered by markets around the world, the impact didn't last long as investors quickly resumed their focus on the deteriorating outlook for China and the global economy.

By midmorning, China's CSI300 index was down 0.5 per cent at 3,028.48 points, while the Shanghai Composite Index was down 1.3 per cent at 2,925.97.

MSCI's broadest index of Asia-Pacific shares outside Japan fell 0.2 per cent in early trade and was just shy of a three-year low hit in the previous session.

Japan's Nikkei was the lone bright spot, rising 1.3 per cent, while Australia fell 0.4 per cent.

Companies such as mining giant BHP Billiton have softened expectations of demand growth from China while countries most exposed to China's economy, such as Indonesia, have dialled down their growth forecasts for 2015 in recent days.

In a sign of how fearful investors have become of risky assets, US stock index futures resumed their descent in early Asian trade with the US S&P 500 mini futures down 0.4 per cent, nearing closer to Monday's 10-month low of 1,831.

Overnight, major US stock indexes shot up after China's policy easing but later gave up all their gains, with the S&P 500 ending down 1.4 per cent.

US stock futures were down 0.2 per cent in Asian trade, suggesting further weakness on Wall Street later in the day.

Fixed income markets were active with investors rushing for cover to government debt and cash. The 10-year note traded to a low yield of 1.90 per cent earlier this week before recovering to trade at 2.06 per cent currently as prices rose. It was close to 2.50 per cent barely a month ago.

"Some parts of the Asian bond markets have become quite illiquid and investors are only buying high-quality paper amid this selloff," said Hayden Briscoe, fixed-income director at AllianceBernstein in Hong Kong and part of a team that manages $250 in assets globally.

The CBOE Market Volatility Index was still elevated at 36, indicating significant uncertainty, even though it was below the previous day's peak of 53.3, which was the highest level since January 2009.

In currencies, the dollar has also broadly lost steam as traders unwound massive carry trade bets in recent years based on higher yielding assets and instead flocked to safe-haven currencies such as euro and yen.

The euro was $1.1529, little changed from late US trade, but more than a full cent above Tuesday's low of $1.1396.

The dollar also slipped back to 118.90, failing to maintain its brief foray above the 120 mark.

Commodity prices hovered just above multi-year lows hit earlier in the week, but concerns that softer demand from China would worsen global supply gluts kept a lid on them.

A 19-commodity Thomson Reuters/Core Commodity CRB Index was just holding above lows not seen since 2003.

Brent crude futures last traded at $43.36 per barrel, about a dollar above 6 1/2-year low of $42.23 on Monday.

The price of copper, often considered a proxy for global economic activity because of the metal's extensive use, bounced 2.3 per cent to $5,065 per tonne. – Reuters