HONG KONG/SINGAPORE (Reuters) - Central banks from Tokyo to Sydney injected extra cash into banking systems or pledged to do so on Friday, as Asia joined a global campaign by monetary authorities to calm panicky credit markets.

"What the central banks are doing is a concerted effort to inject liquidity. And the worrying thing is that they do that when the system is not functioning the way it should," said Jimmy Koh, a currency strategist at United Overseas Bank.

The moves came after the European Central Bank injected record amounts of cash to prevent a financial system seizure after European banks essentially stopped providing short-term funds to one another on Thursday. The U.S. Federal Reserve also injected cash on a smaller scale.

The trigger was news that France's biggest listed bank, BNP Paribas (Paris:BNPP.PA - News), had frozen $2.2 billion worth of funds hit by U.S. subprime mortgage woes, further increasing fears the subprime problems would squeeze credit

TOKYO (AP) -- Asian stocks fell sharply in early trading Friday following steep declines in U.S. stocks over fears of spreading turmoil from subprime mortgages.

The Nikkei 225 index fell 448.64 points, or 2.61 percent, to 16,721.96 during the morning session on the Tokyo Stock Exchange. The broader Topix index of all shares on the exchange's first section sank 48.94 points, or 2.91 percent, to 1,634.87.

The Korea Composite Stock Price Index fell as much as 70.33 points, or 3.7 percent, to 1,838.35 before rebounding slightly.

The plunge came after the Dow Jones industrial average fell 387.18, or 2.83 percent, to 13,270.68 in New York on Thursday after a French bank announced it was freezing funds that invested in U.S. subprime mortgages, deepening fears