Stocks rose in the United States and Europe and the dollar hit a three-week high against the euro after European Central Bank President Mario Draghi said further rate cuts were being considered to stimulate the euro zone economy.
The ECB, as widely expected, took no new steps on Thursday, but Draghi signaled that it could extend its €1 trillion bond-buying quantitative easing program if necessary to combat weak inflation.
"We are ready to act if needed ... and we are open to the full menu of monetary policy," Draghi told a news conference.
Worries that global economic growth is slowing, particularly in China, have depressed stock and commodity markets across the world in recent months and prompted a series of downgrades to economic forecasts from the International Monetary Fund and others.
Wall Street rallied, gaining ground after the ECB news and earnings reports that included better-than-expected results from McDonald's Corp and weak figures from Caterpillar.
A global index of equities rose 0.8%.
The Dow Jones industrial average jumped 320.55 points, or 1.87%, to 17,489.16, the S&P 500 gained 33.57 points, or 1.66%, to 2,052.51 and the Nasdaq Composite added 79.93 points, or 1.65%, to 4,920.05.
The dollar rose 1.4% against a basket of currencies. The U.S. unit has been losing ground in the past month as expectations waned for an interest rate hike this year by the Federal Reserve.
The euro fell 1.8% after the ECB decision and moving sharply lower after Draghi's comments, trading at $1.1107, a three-week low. It also fell to a one-month low against sterling. Against the yen, the dollar was up 0.5% to 120.73 yen.
"Draghi delivered all kinds of dovish signals, which weighed on the euro," said Vassili Serebriakov, currency strategist at BNP Paribas in New York. "He was as dovish as can be without changing policy."
The pan-European FTSEurofirst 300 stocks index rose 2.1%. An increased full-year sales outlook from Swiss drugmaker Roche helped support the index. The company's shares rose 2.9%.
Earlier, MSCI's broadest index of Asia-Pacific shares outside Japan slipped 0.2%. Japan's Nikkei closed down 0.6%.
Euro zone government bonds rallied, with benchmark German 10-year Bund yields falling to 0.49%, down 0.07 percentage point.
U.S. Treasury yields were little changed, with the 10-year note yield flat at 2.028%.
Oil prices were flat. Brent, the global benchmark, was last up 36 cents at $48.21 a barrel. U.S. crude fell 21 cents to $45.40 a barrel.
Gold held near its lowest in more than a week, last trading at $1,166 an ounce.