NEW YORK — But can it last?

After suffering the worst drubbing in its 112-year history last week, the Dow Jones industrial average leaped more than 900 points yesterday — its biggest one-day point gain — as investors were encouraged by a series of aggressive steps by central banks to shore up the global banking system.

But doubts lingered about whether the rally would have staying power, especially given the troubles afflicting global credit markets and the U.S. economy. Some fretted that it could be what Wall Street likes to call a "sucker's rally" — a big gain in the midst of a bear market that gets investors' hopes up, only to dash them with further declines.

"There's just so much more that has to be remedied … that it's unlikely that we've hit bottom," said Bill King, market strategist at M. Ramsey King Securities in Burr Ridge, Ill. "We haven't seen the economic ramifications of all this financial destruction — and we will."

For at least one day, though, investors had reason to cheer. They piled into stocks after European governments emerged from a series of emergency weekend meetings to pledge guarantees for interbank lending and establish direct equity stakes in battered financial institutions.

The U.S. government is expected today to reveal details of its own plan — first announced in broad form Friday — to take equity positions in U.S. banks and of its other measures to shore up the nation's troubled financial system. Details that leaked last night hinted at a European-style approach of stronger protections, which could provide another boost for stock prices today.

Yesterday, the Dow rocketed up 936.42 points, or 11.1 percent, to 9,387.61, erasing half of last week's 18 percent loss. That easily topped the widely watched average's previous record of 499 points in one day, and it marked the biggest percentage increase since the depths of the Great Depression in 1933 — even topping the 10.2 percent gain two days after 1987's infamous Black Monday crash.

OPTIMISTIC BUT WARY

The rally was "an upward thrust of massive proportion that indicates to me that the market has had a huge dose of oxygen," said David Kotok, chief investment officer of money manager Cumberland Advisors in Vineland, N.J. "It's likely the market will be volatile but will head higher for the rest of the year."

From its intra-day low Friday, the Dow rebounded more than 1,500 points yesterday. That prompted some analysts to conclude that the market was near its bottom — the point where all sellers have gotten out and buyers have moved in, setting the stage for a sustained advance.

Other market watchers, however, echoed King's concern that the rally could be little more than a one- or two-day affair.

Throughout the housing crisis and credit crunch that began last year, the market has had several explosive one-day rallies, only to see them overwhelmed by renewed waves of selling when problems in the financial system and the economy proved intractable.

The latest episode came barely two weeks ago, when the Dow jumped up 485 points the day after a record-setting 777-point drop. The Dow then plummeted almost 2,400 points over the next eight days.

CREDIT A KEY INDICATOR

Beyond that, many experts say the beleaguered credit markets — not the volatile stock market — are the real litmus test of financial-market health in the current crisis.

The credit markets have gone into a deep freeze as banks have become wary of lending to each other, as well as to businesses and consumers. Economists fret that the breakdown in the flow of credit is putting the clamps on business and consumer spending and pushing the economy into recession.

Yesterday, interbank lending rates eased a bit in Europe, but they remained extraordinarily high. The U.S. Treasury market was closed for the Columbus Day holiday, meaning a key test of the financial markets' reaction to the latest bank rescue plans was delayed until today.

"The essential problems in the market are with the credit market," said Joe Saluzzi, co-head of equity trading at Themis Trading in Chatham, N.J. "The stock market is an irrational beast that goes on through the day playing off fear and emotion."

Experts also pointed out that markets often "retest" their lows. After the initial burst of euphoria subsides, stock prices often retreat until investors are convinced that economic and financial conditions truly are brightening.

The Dow remains almost 34 percent below the all-time closing high of 14,164.53, reached a year ago last week.

ASIAN STOCKS CLIMB

Asian markets soared for a second day today, led by a record 14 percent jump in Tokyo. Japan's benchmark Nikkei 225 index surged 1,171.14 points, or 14.15 percent, to close at 9,447.57 — a stunning reversal after plunging nearly 10 percent Friday and its biggest single-day gain in history. Tokyo financial markets were closed yesterday for a holiday.

In Australia, the S&P/ASX200 index traded 3.7 percent higher as the government announced a plan to inject about $7.4 billion to stimulate the country's slowing economy.

Hong Kong's key index gained 3.5 percent, while South Korea's market jumped more than 6 percent. The Philippine market surged more than 7 percent and Indonesia's market — shut half of last week due to huge declines — was up more than 6 percent.

Although the multiple government efforts fell short of the unified global approach that many had hoped for, investors were encouraged by the idea of injecting capital directly into banks.

"The latest moves have met the market's approval, which is something the other moves couldn't do," said Jack Ablin, chief investment officer of Harris Private Bank in Chicago. "It feels great to be able to watch the market and see it go up substantially."