By Min Zeng

Government bond yields on both sides of the Atlantic tumbled to historic lows on Friday, the latest ripple from Thursday's decision by the European Central Bank to support economic growth with a monetary stimulus plan.

The 10-year yields in Germany, France, Belgium, Finland, Austria, the Netherlands, Spain, Italy, Ireland and Portugal all fell to record lows, extending the declines of the past months.

In the U.S., the yield on the benchmark 10-year note fell toward a 20-month low. The yield on the 30-year Treasury bond settled at a record low. Bond yields fall when their prices rise.

Investors have been piling into both stocks and government bonds following ECB President Mario Draghi's announcement on Thursday that the central bank will buy a total of EUR60 billion ($67 billion) a month in assets, including government bonds. The ECB said the buying will start in March and run through September 2016.

Bond buyers believe the buying binge by the ECB will boost asset prices at a time when demand for bonds, especially high-grade government bonds, remains strong due to the uncertain global growth outlook.

"In today's $100 trillion global supermarket of bonds, the shelves will be further emptied by the ECB's bond-buying program, supporting bond prices," said Tony Crescenzi, senior market strategist at Pacific Investment Management Co. in Newport Beach, Calif., which had $1.68 trillion in assets under management at the end of 2014.

Lower yields on government bonds could be a boon for the housing market as they push down mortgage rates. Companies also benefit by locking in favorable borrowing costs when selling new debt.

But lower yields mean investors have to make do with lower income, pushing many to dial in to riskier bonds for higher yields. Investors also caution that bond buyers may be vulnerable if sentiment sours on bonds, as slim yields offer a thin layer of protection against the risk of capital losses.

In late afternoon trading, the yield on the benchmark 10-year Treasury note was 1.814%, compared with 1.898% on Thursday. The yield had closed at 1.777% on Jan. 15, the lowest level since May 2013. The yield was 2.173% at the end of 2014.

The yield on the 30-year Treasury bond closed at 2.391%, breaking below the previous record of 2.399% on Tuesday.

The ECB joins the ranks of the Federal Reserve and other major central banks in tapping the unconventional monetary-policy tool, known as quantitative easing, following the 2008 financial crisis.

The yield on the 10-year German government bond fell Friday to 0.316%, according to Tradeweb. The yield on France's 10-year bond fell to 0.533%. The yield on Spain's 10-year bond declined to 1.378% and the yield on Italy's 10-year bond dropped to 1.538%.

Jim Caron, global fixed-income portfolio manager at Morgan Stanley Investment Management, with $398 billion in assets under management, said he expects the ECB to gobble up all the net issuance of eurozone government bonds over the next 12 months.

"This should prove to be supportive for euro bonds ultimately," said Mr. Caron. "As for Treasury bonds, they will follow price action in Europe."

Lower bond yields in Europe and Japan have turned U.S. Treasury bonds into an attractive bargain, dragging down U.S. bond yields even as the U.S. economy has strengthened and the Fed is prepared to raise interest rates in the middle of this year for the first time since 2006. The Fed's next policy meeting is due on Jan 27-28.

A stronger dollar has enabled foreign investors to pick up extra returns on U.S. bonds and stocks. The dollar rallied Friday to the strongest level against the euro in more than a decade.

Some investors are seeking higher yields in riskier markets.

Mark Dowding, senior fixed-income manager at BlueBay Asset Management in London, which oversees $67 billion, said he has allocated more cash into government bonds sold by relatively small economies in Europe, such as Latvia, Lithuania, Slovakia and Slovenia.

Mr. Dowding has also been buying euro-denominated government bonds sold by such countries as Mexico, Brazil, Turkey and Indonesia.

"At some point we believe everyone is too pessimistic on growth and yields will start to rise, but this is more likely later in 2015," said Mr. Dowding.

 
   COUPON  ISSUE   PRICE      CHANGE   YIELD     CHANGE 
   5/8%    2-year 100 8/32    up 1/32  0.499%     -2.4BP 
   7/8%    3-year 100 1/32    up 4/32  0.859%     -4.0BP 
   1 5/8%  5-year 101 14/32   up 9/32  1.323%     -5.7BP 
   2 1/8%  7-year 103 9/32    up 15/32 1.620%     -7.0BP 
   2 1/4%  10-year 103 29/32  up 24/32 1.814%     -8.3BP 
   3%      30-year 112 29/32  up 1 25/32 2.391%   -7.8BP 

2-10-Yr Yield Spread: +131.5BPS +137.4BPS

Source: Tradeweb/WSJ Market Data Group

-- Write to Min Zeng at min.zeng@wsj.com

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