The Bank of Japan said it pumped 4.0 trillion yen (40 billion dollars) into the Tokyo money market Thursday, the biggest one-day injection since the credit crisis began.

It was the 17th straight business day that the Japanese central bank has poured money into the markets to try to ensure a flow of credit - the lifeblood of the global economy.

The stepped-up action came a day after the Tokyo stock market suffered its biggest loss in two decades, plunging more than nine percent. Stocks rebounded Thursday to show a gain of 1.5 percent by mid-afternoon.

Central banks in the United States, Canada and Europe on Wednesday slashed interest rates in a coordinated effort to calm the worst financial crisis since the Great Depression.

The Bank of Japan did not join the concerted rate cut action, saying its benchmark lending rate was already low at

0.5 percent.

Japanese financial institutions have been relatively immune to the global credit crisis, seizing the opportunity to expand overseas, buying stakes or assets from troubled Western banks.

But the Japanese stock market has been hard hit, with the Nikkei index down about 30 percent since the start of August. There are also growing concerns that the Japanese economy may have already slipped into a recession.

Some analysts believe the BoJ may have to reduce official borrowing costs at some point if the economy keeps worsening, but others disagree.

"We believe the Bank is unlikely to cut rates," said Barclays Capital's chief Japan economist, Kyohei Morita.

He said Japanese policymakers had other policy tolls at their disposal, such as paying interest on current account deposits or lowering the Lombard rate at which commercial banks can borrow directly from the BoJ.