LONDON (AP) — Global stocks took another pounding Monday as worries over the downgrade of U.S. debt outweighed relief at the European Central Bank’s purchase of Italian and Spanish bonds to help the two countries avoid devastating defaults.

The world’s leading financial policymakers said they were ready to act to contain the uncertainties in the markets, but that did not ease the concerns of stock market investors. The European Central Bank’s risky decision to buy Italian and Spanish bonds helped ease selling pressure in Europe, but only temporarily as the main worry remained centered on Standard & Poor’s momentous decision to lower its triple A rating for the U.S.

“The traditional market saying that you don’t catch a falling knife is certainly relevant here, with many investors not willing to take any risks at the moment,” said Giles Watts, head of equities at City Index. “We need an air of calm in the markets to help combat this but it’s hard to see when that will come given the severity of the falls we are seeing.”

In Europe, Britain’s FTSE 100 index of leading British shares closed down 3.4 percent at 5,068.95, while France’s CAC-40 slid 4.7 percent to 3,125.19. Germany’s DAX tumbled a further 5 percent at 5,923.27.

Greece’s main stock market was the worst-performing in Europe, closing down 6 percent at 998.24 — its lowest level since January 1997. Less than an hour after the stock exchange closed, the Capital Market Commission imposed the two-month ban on short-selling, which comes into effect as of Tuesday.

On Wall Street, the Dow Jones industrial average was down 2.6 percent at 11,140 while the broader Standard & Poor’s 500 index fell 3.3 percent to 1,159.

The decline in appetite for risk was evident elsewhere. Traditional safe havens like the dollar and the Swiss franc remained strong while the euro was sold off heavily.

So far, the S&P downgrade doesn’t seem to be having too much of an impact on U.S. government bonds. The worry has been that the downgrade would prompt investors to demand more, but the yield on ten-year Treasuries has actually fallen.

“Early market reactions suggest that the treasury market will remain well supported,” said Jane Foley, an analyst at Rabobank International. “Even though there may be no sharp sell-off in treasuries this week, S&P’s decision should at least provide a signal to the U.S. government that it may be foolhardy to continue to take its creditors for granted indefinitely.”

In Europe, a particular focus has also been on the bond markets and the ECB’s statement late Sunday that it would “actively implement” its bond-buying program to calm investor concerns that Italy and Spain won’t be able to pay their debts. Last week, worries over the two countries’ ability to keep tapping bond markets contributed to the turmoil in global markets.

Traders said the European Central Bank spent around 2 billion euros, and the yield on Italy’s ten-year bonds fell 0.70 percentage point to 5.30 percent while Spain’s tumbled 0.90 percentage point to 5.14 percent.

Seeking to avert panic spreading across financial markets, the finance ministers and central bankers of the Group of 20 industrial and developing nations issued a joint statement Monday saying they were committed to taking all necessary measures to support financial stability and growth.

“We will remain in close contact throughout the coming weeks and cooperate as appropriate, ready to take action to ensure financial stability and liquidity in financial markets,” they said.

However, many analysts think that the international efforts may not be enough to calm jittery markets.

“Investors are concerned about a rising risk of global recession, credit downgrades especially now in the eurozone, such as France, the threat of a major bank bust and a global liquidity trap as investors stay in cash,” said Neil MacKinnon, global macro strategist at VTB Capital.

Earlier in Asia, the repercussions of S&P’s downgrade weighed on stock markets.

Among the major markets, Japan’s Nikkei 225 stock average closed down 2.2 percent 9,097.56, while Hong Kong’s Hang Seng fell the same rate to 20,490.50. South Korea’s Kospi ended 3.8 percent lower as did China’s main exchange in Shanghai.

In the currency markets, the euro was down 0.6 percent at $1.4224 while the dollar was down 1 percent at 77.54 yen. The U.S. dollar also hit another record low against the Swiss franc.

Fears over the global economy are having a major impact on oil markets too, with the main New York rate down another $2.78 to $84.12 a barrel.