Jeffrey Gundlach, chief executive of DoubleLine Capital, said on Friday that investors are dropping risky assets from their portfolios because of falling global gross domestic product expectations, fueled by China's slowing growth, and the intensifying U.S. presidential race.

"Falling global GDP expectations, fueled by China having trouble holding it together, are affecting financial markets," Gundlach said in an email to Reuters. "And then, there's the unfolding Trump 'victory scare narrative.'"

On Friday, global growth worries and a sharp drop in oil prices sent jitters through Wall Street, leading the three major U.S. indexes lower for the second straight day on Friday.

The yield on the U.S. Treasury note plunged to 1.633 percent, its lowest since February 11, on Friday.

"If the 10-year Treasury note's yield breaks below the three-year resistance, then it is a big game changer," Gundlach said. He said he did not think it would happen on Friday but could do so in coming weeks.

Copper is "almost on the 12-month low, the global economy must be weak and stocks look scary," Gundlach said.

Brexit fears and mixed messages from Federal Reserve officials are adding to the risk aversion in financial markets. Britain will vote on a referendum on June 23 to decide whether the country should remain in the European Union.