Investors readying for a rise in global liquidity initially lifted U.S. Treasuries, whose relatively rich yields grew more attractive with prospects of lower euro zone bond yields, before prices turned lower.
"It's likely to impact yields everywhere," said Aaron Kohli, an interest rate strategist at BNP Paribas in New York. "When you put this much stimulus into the markets, it's going to go other places that you hadn't intended, and one of those places is going to be U.S. debt."
The ECB's program to buy euro-zone government bonds, along with its existing schemes, will pump 60 billion euros a month into the euro zone economy. It is set to run from March until September 2016.
ECB President Mario Draghi made clear the plan could be extended if the bank felt that was necessary.
Robust U.S. economic data added to gains on Wall Street, where the Dow Jones industrial average <.DJI> provisionally ended ahead 260.6 points, or 1.48 percent, at 17,814.88, the S&P 500 <.SPX> rose 31.08 points, or 1.53 percent, to 2,063.2, and the Nasdaq Composite <.IXIC> added 1.78 percent to 4,750.40.
Thursday's gains turned the S&P and Nasdaq index positive for 2015 to date, with banks leading the gains.
Europe's pan-regional FTSEurofirst index <.FTEU3> ended up 1.6 percent, as Scandinavia and eastern European markets rose in tandem. London's top stock index <.FTSE> added 1 percent and touched a four-month peak in a sixth straight winning session.
As the euro slumped to a nadir of $1.1318 last touched in September 2003, an index that measures the dollar against six of the world's main currencies <.DXY> rose 1.6 percent. The euro <EUR=> was last at $1.1339.
Denmark's crown <EURDKK=D3> tumbled against the euro after the country's central bank cut its key rate to a record low -0.35 percent from -0.20 percent.
The benchmark 10-year Treasury note <US10YT=RR> was off 6/32 and yielding 1.8717 percent, after falling as low as 1.81 percent, down from 1.94 percent before the ECB's announcement. The 30-year <US30YT=RR> yielded 2.4440 percent, reflecting a price decline of 4/32, after going as low as 2.40 percent, down from 2.54 percent before the announcement.
German 10-year government bond yields <DE10YT=RR> hit record lows of 0.377 percent as European government borrowing rates plummeted.
Oil and gold <XAU=> prices bounced around as hopes that the ECB's action would boost growth contended with the threat of a stronger dollar, which would put pressure on products priced in the U.S. currency. <O/R>
Brent and U.S. crude futures gave up earlier gains to fall to $48.86 <LCOc1> and $46.59 per barrel <CLc1>. Gold <XAU=> was up nearly 1 percent to $1,305.30 an ounce.
(Reporting by Michael Connor in New York; Editing by James Dalgleish and Leslie Adler)
By Michael Connor