Many bond investors also moved on from disappointment over the Fed's overnight move to the likelihood that the central bank might take more action in the future.

MSCI's broadest index of Asia Pacific shares outside Japan fell 1.4 percent.

The US central bank, as expected, extended its "operation Twist" stimulus programme on Wednesday, under which it sells short-term securities to purchase longer-dated ones and bring down longer-term borrowing costs. The central bank did not signal a third round of quantitative easing as some had hoped, but the statement from its policy-setting Federal Open Market Committee said it was "prepared to do more."

The Fed has already purchased $2.3 trillion in debt in two earlier rounds of quantitative easing, and Wall Street's top bond firms still see a 50 percent chance there will be a third round.

Providing incentive for possible future action, the Fed also cut its US economic growth estimates this year to a range of 1.9 percent to 2.4 percent, down from its April forecast of 2.4 percent to 2.9 percent.

"The Fed had to do something to recognize those three or four bad employment reports, which they did, and they said they will do more if needed," said a trader at a European brokerage in Tokyo. "They've done 'shock,' but they still need to have some 'awe' left, with Europe still working out their problems."

The latest test of investor confidence that European countries can fund their debt burden will come later on Thursday, when Spain is due to sell up to 2 billion euros of two-, three- and five-year bonds.

The yield on US 10-year notes edged down to 1.63 percent from 1.64 percent in late US trade, but remained above 1.61 percent in Tokyo on Wednesday.

The yields on 30-year bonds stood at 2.71 percent, down slightly from 2.72 percent in late US trade and also in Tokyo trade on Wednesday.