Traders dumped stocks and commodities across the globe in favor of safehaven assets including German Bunds, yen and gold.
Benchmark 10-year Treasuries notes were last up 17/32 in price for a yield of 1.990 percent, down 6 basis points from late on Friday.
The 10-year yield fell as low as 1.9460 percent in early US trading, which was the lowest level since April 28, according to Reuters data.