Treasury bonds gained Monday, extending the biggest weekly rally in more than a month. The yield on the benchmark 10-year note approached the lowest level in more than six months set last week. Traders said the factors that support bond prices remain in place: uneven global economic growth, the prospect that major central banks will keep interest rates low for longer, and concerns about valuations of U.S. stock prices.

In Monday trade, the 10-year Treasury note was 3/32 higher, yielding 2.507%, according to Tradeweb. The yield touched 2.472% during last Thursday’s session, the lowest level since Oct. 30.

When bond prices rise, their yields fall.

On Monday, U.S. stock futures were lower and European equities pulled back. Stocks in China sold off amid concerns about the waning momentum of the world’s second-largest economy.

Anthony Cronin, a Treasury bond trader at Société Générale SA, said catalysts to send bond yields lower could come from further monetary stimulus from the European Central Bank, “weaker data in the U.S. and escalation of tensions between both Russia and Ukraine as well as China and Vietnam.”

Some traders said the sharp decline in yields was overdone, and in the short term, it may be difficult for the yield to break below 2.47%. On Friday, bond yields rose as investors cashed out some chips.

“If we don’t get through 2.47%, it is just range-bound trading” in the near term, said Larry Milstein, head of government and agency trading at R.W. Pressprich & Co. in New York. Mr. Milstein expects the 10-year yield to trade between 2.47% and 2.6% in the short term. The yield could drop to as low as 2.25% if it breaks below the 2.47% level, he said.

Bond yields may have room to fall if bond bears cave in and abandon their wagers betting on bond yields to rise later this year. The 10-year yield has dropped from about 3% at the start of the year, and pressure is mounting on investors and traders still betting on higher yields, known as shorts.

Short bets have been dialed back recently as bond yields declined. Investors holding shorts need to buy back bonds as the market turns the other way, further boosting bond prices and sending yields lower.

But many bond bears still expect yields to rise later this year as the U.S. economy picks up speed.

Goldman Sachs Group Inc. expects the 10-year yield would rise to 3.25% at the end of this year. Morgan Stanley expects a 3.3% yield.

By Min Zeng