Investors savoring blockbuster gains amid a roaring market rally have been ignoring the risks piling up across global markets, allowing potential problems to permeate, warned Howard Marks, head of the world’s largest distressed-debt firm.

“We are living in a difficult, low-return world that has been ignoring risk incidents," Marks, the co-chairman of Oaktree Capital Group LLC, said in a telephone interview. “When the market shrugs off its problems, it is not a plus, as that permits problems to accumulate. Up-cycles don’t go on forever.”

Marks was the latest high-profile investor to sound caution, after Janus Capital Group Inc.’s Bill Gross and DoubleLine Capital LP’s Jeffrey Gundlach said sovereign bonds, with yields at record lows, were too risky.

But with global central banks continuing to prop up higher-yielding assets, investors have shrugged off sluggish economic growth and Britain’s vote to leave the European Union to fuel a global rally across stocks and bonds. The speculative-grade bond market that was accompanied by doomsday calls coming into 2016 has been on a tear, with gains surpassing 12 percent for the year.

Low interest rates around the world have created a rush for risk assets and high-yield bonds look very good in relative terms, Marks said, even though there are no “compelling” buys. A rebound in oil prices underpinned the rally in the debt that lost 4.6 percent last year. Energy company debt -- one of the largest sub-groups in the asset class -- gained more than 55 percent since the commodity bottomed in February, Bank of America Merrill Lynch index data show.

“The issue that people face is that money has to go someplace," he said. “It’s not practical to put it under the mattress."

If investors do want to jump into less-liquid assets in their hunt for yield, they need to be willing to ride out the rough times, he said.

“When you go into risk assets and they go through a tough period, there will be heartburn and price declines,” he said. “If you are going to need the money in the short term, you shouldn’t put it into potentially illiquid assets."