Faltering confidence in the financial system, undermined by a series of bank bailouts, was precipitating the measures, analysts said, since a failure to match guarantees by Ireland, France, Greece and Sweden could risk a massive fund outflow. Yet the guarantees themselves raised questions about their potential impact on government finances, and showed European governments were unable to find a unified approach despite a weekend summit where they agreed to do just that.
"Governments have no choice but to give the guarantees on deposits, otherwise we will see runs on banks and a complete loss of business and consumer confidence," said Neil Mackinnon, chief economist at ECU Group.
"The stakes have never been higher," he added.
Markets responded to the disarray by sinking rapidly, following selloffs in Asia. Russia shut down both its stock markets after they fell more than 15 percent. Germany's DAX was down 428.04, or 7.4 percent, at 5,368.99, while France's CAC-40 was 350.74 points, or 8.9 percent, lower at 3,730.01. The CAC's fall in afternoon trading exceeded the record one-day decline of 7.39 percent from Sept. 11, 2001.
The FTSE 100 index of leading British shares was down 269.30 points, or 5.5 percent, at 4,601.04.
Wall Street took its cue from Europe, with the Dow Jones industrials down 430.81 points, or 4.2 percent at 9,907.55 amid growing fears that the credit crisis is spreading around the world.
Meanwhile, the euro slid below the $1.36 mark for the first time in over a year.
The crisis engulfing Europe and its markets has fueled talk of coordinated interest-rate cuts by the world's leading central banks, possibly as early as Monday.
Analysts said they wouldn't be surprised if the U.S. Federal Reserve, the European Central Bank and the Bank of England instigate the first joint action on interest rates since the September 2001 terrorist attacks on the U.S.
"I think we will see interest-rate cuts this week," said ECU Group's Mackinnon.
So far, the banks have continued to flood the money markets with additional liquidity. On Monday, the ECB injected another $50 billion into money markets while the BoE added another $10 billion.
The Swedish Central Bank increased its lending to 100 billion kronor ($14.2 billion).
Additionally, the Fed said that 28-day and 84-day cash loans being made available to banks will be boosted to $150 billion each, effective Monday. Those increases will eventually bring the amounts outstanding under the program to $600 billion.
British Prime Minister Gordon Brown planned a call to Merkel to discuss the crisis, and Britain's Treasury chief, Alistair Darling, was due to make a statement to Parliament later. So far, Britain has raised its deposit guarantee only to 50,000 pounds ($87,900), but was under pressure to guarantee all deposits.
French President Nicolas Sarkozy spoke by telephone in the morning with Brown, ECB President Jean-Claude Trichet and European Commission President Jose Manuel Barroso and was due to speak to Merkel later too.
"We need a coordinated response," Sarkozy said during a visit to a Renault car plant in Normandy. Meanwhile European Union finance ministers were set to begin two days of talks on the crisis in Luxembourg.
"This is a very serious situation and one that needs to be addressed," said EU spokesman Johannes Laitenberger.
"Obviously there is a great effort under way. Nobody is suggesting that this is business as usual, but it's true that there is not one single magic bullet that will solve this."
The renewed effort to coordinate a response came after the weekend commitment by Europe's four leading economic powers - Germany, France, Britain and Italy - to work together. That commitment fell apart on Sunday when Merkel announced that all 568 billion euros ($786 billion) worth of private deposits held in Germany would be guaranteed, alongside a new 50 billion euros ($69 billion) bailout package for Hypo Real Estate AG, Germany's second-biggest mortgage lender.
"The EU is liable to be exposed as a fair weather construction, lacking the means of swift response and the hold over its citizens' loyalties to survive really adverse conditions," said Stephen Lewis, an analyst at Monument Securities.
In a joint statement Monday, Merkel and Finance Minister Peer Steinbrueck said the guarantee was "an important step at the right moment."
In response to the German move, the Danish Economy Ministry said commercial lenders had agreed to contribute up to 35 billion kroner, or about $6.4 billion over two years to a fund that will help insure account holders from losses. Austrian officials have indicated they might join in as well.
That was followed this afternoon by Iceland's guarantee of all deposits after trading was halted in six bank stocks. Icelandic banks' assets dwarfs the rest of its economy and its currency has fallen sharply in the past week.
The markets are skeptical that Europe's piecemeal response to the crisis so far will work to stem the selling tide.
"The main problem for Europe is that a coordinated response has proved impossible to reach, and the case-by-case approach that has so far been applied has clearly failed to restore confidence," said Dragana Ignjatovic, European analyst at Global Insight.
Meanwhile, Iceland halted trading in six bank stocks while the government drafted a crisis plan. Icelandic banks' assets dwarfs the rest of its economy and its currency has fallen sharply in the past week.
