Asian shares were pressured on Wednesday as a sharp boost to asset prices inspired by the U.S. Federal Reserve's aggressive stimulus gave way to worries about Spain's fiscal strains and deteriorating corporate profits.

Riskier assets spiked after the Fed launched a third round of bond buying known as quantitative easing last week, but have consolidated this week as investors now contemplate whether global central bank stimulus efforts can effectively revive demand to underpin economic activity.

A Thomson Reuters/INSEAD survey on Wednesday underscored such concerns, showing business sentiment among Asia's top companies fell for the second straight quarter, dragged down by export-orientated economies such as China and Japan, while domestic spending helped boost Southeast Asia's outlook.

MSCI's broadest index of Asia-Pacific shares outside Japan <.MIAPJ0000PUS> traded flat to down as much as 0.2 percent, with South Korean shares <.KS11> leading the decline with a 0.5 percent drop while Australian shares <.AXJO> edged up 0.3 percent and Hong Kong shares <.HSI> also rose 0.3 percent.

The Nikkei stock average <.N225> was up 0.2 percent, with investors buying back battered China-related stocks as the Sino-Japan tension has not worsened from the previous day. <.T>

U.S. stocks ended flat to slightly lower while European shares fell on Tuesday as Spain kept skirting around decisions on whether to seek an European Union bailout, which is conditional for the European Central Bank to start buying the country's bonds to tame its borrowing costs.

"It's probably not the start of a new downturn, but I do wonder whether the markets very quickly discounted the ECB and the Fed and now back to looking at the same old question that is Spain - will they or won't they ask for a bailout and what kind of conditions would be applied to it. And whether the U.S. economy can get out of the 1.5-2 percent growth range," said Adrian Foster, head of financial markets research for Asia-Pacific at Rabobank International in Hong Kong.

"I doubt those questions are going to get answered anytime soon, so maybe a one-off repricing as a result of the ECB and Fed action, and then beyond that, we are back at the whims of going up and down 1-2 percent a day," Foster said, adding that the liquidity pumped in by central banks amplify market swings as the ample liquidity remains in the financial system rather than trickling into the real economy.

U.S. Treasury bond prices rose on Wednesday on bargain hunting from last week's sharp sell-off and renewed bids for safe-haven assets, as concerns grow over global growth slowdown while Spanish yields stayed under upward pressures on the uncertain outlook for Spain's fiscal woes.

The euro steadied around $1.3047.

Commodities were mixed, with London copper down 0.1 percent to $8,307.75 a metric ton, as traders reported fading interest from top consumer China, with prices near their highest in more than four months touched after the Fed.

Oil futures were mixed, with U.S. crude up 0.3 percent to $95.58 a barrel and Brent crude down 0.1 percent at $111.96. Brent futures were hurt by the fragile global economy and indications that the world's top oil exporter Saudi Arabia was pumping more oil to bring down prices.

"The anticipation is that the Chinese economy is going to remain weak and it's going to take some time before we start to see a turnaround," said Ric Spooner, chief market analyst at CMC Markets in Sydney.

Spot gold fell 0.3 percent to $1,766.94 an ounce.

BOJ AWAITED

The Bank of Japan ends its two-day policy meeting this session.

Views were mixed about whether the BOJ will follow its peers overseas with action, after the Fed launched a third round of bond buying known as quantitative easing (QE) last week and the ECB earlier this month outlined its bond-buying scheme to ease fiscal strains for euro zone countries seeking assistance.

Some in the markets speculate the BOJ might announce fresh steps to avoid a plunge in Japanese shares and the yen's appreciation ahead of the September 30 fiscal-half. Trade with China was certain to be hit hard by the violent anti-Japanese protest escalating over a territorial dispute, at a time Chinese power transition is taking place, analysts said.

"Along with the Chinese factor, the Nikkei faces downside risks as global equities look vulnerable to adjustments from the post-Fed rally, and it's possible for the BOJ to pre-emptively step in to bolster sentiment ahead of the fiscal half, where the level of stock prices is crucial for companies," said Yuji Saito, director of foreign exchange at Credit Agricole in Tokyo.

"Many domestic players think the BOJ will stand pat and wait until October, while foreign players see some BOJ move today," Saito said, adding that no action could push the dollar down to 78 yen or briefly below 78 where stop orders were lined up.

Concerns over the territorial conflict and damage to trade with China will limit the downside for the dollar/yen, he said.

The dollar fell 0.2 percent to 78.62 yen.

Sentiment was cautious in Asian credit markets, with the spread on the iTraxx Asia ex-Japan investment-grade index widening by 2 basis points, but still near a 14-month low.

(Additional reporting by Luke Pachymuthu; in Singapore; Editing by Michael Perry & Kim Coghill)