Japan's central bank has expanded its monetary easing by 10 trillion yen.
The move is aimed at nurturing the country's feeble economic recovery and cushion its exporters from the yen's rise against other currencies.
The Bank of Japan wrapped up a two-day policy meeting by increasing its asset-purchasing fund to 55 trillion yen from 45 trillion yen.
That followed the US Federal Reserve's decision last week to stimulate growth through so-called quantitative easing.
The bank also eliminated the 0.1% floor for interest rates on Japanese government bonds it purchases.
It hopes that that will help to stabilise the yen, said Masayuki Kichikawa, an economist at Bank of America-Merrill Lynch.
He characterised the Bank of Japan's move as a "pleasant surprise" since the central bank had not been expected to ease policy until late October.
Recent weak economic data and strong pressure from politicians anxious to not to see a further deterioration ahead of elections, expected soon, may have played a role.
The US Federal Reserve, similarly alarmed by chronic weakness in the US economy, launched an aggressive new effort to boost the stock market and make borrowing cheaper for years to come.
The Fed said it would buy mortgage bonds for as long as it deems necessary and keep interest rates at record lows until the middle of 2015, six months longer than previously planned.
Japan has been wrestling for years with deflation, or falling prices, which can be a drag on economic growth. The rapid ageing of the population has made the effort to break free from the prolonged bout of deflation doubly difficult.
"It shows they are co-operating to end deflation as soon as possible," Kichikawa said. The move to eliminate the floor for rates on interest-bearing bonds was likely to have more impact than the 10 trillion yen increase in asset purchases, he said.
Recent credit-easing steps by central banks
BANK OF JAPAN
Interest Rates - benchmark interest rate has been kept at zero to 0.1%.
Bond Buying - Announced today that it will boost the size and duration of a government bond-buying programme that is intended to encourage borrowing and spending and make Japan's exports more competitive. It also eliminated a minimum required interest rate on the government bonds it buys.
US FEDERAL RESERVE
Interest rates - Has kept its benchmark short-term rate at a record low near zero since December 2008. Last week, it said it planned to maintain that level at least unti the middle of 2015 - six months longer than previously planned.
Bond buying - It said last week that it will spend $40 billion a month to buy mortgage bonds for as long as it deems necessary to make home buying more affordable. It also said it would try other stimulative measures if hiring does not pick up.
EUROPEAN CENTRAL BANK
Interest rates - Has kept its benchmark rate at 0.75%, a record low.
Bond buying - Unveiled this month a plan to buy unlimited amounts of government bonds to help lower borrowing costs for countries struggling to manage their debts. Earlier, the ECB gave banks more than €1 trillion in low-interest loans lasting up to three years. The loans provide secure financing at a time when some banks can not borrow normally.
BANK OF ENGLAND
Interest Rate: Has kept its benchmark rate at a record low of 0.5% since 2009.
Bond buying: Announced this summer a plan to buy more government bonds from financial institutions, hoping the banks will use the extra cash to lend to businesses and households.
