WASHINGTON (AP) — Average long-term U.S. mortgage rates were unchanged this week, but remained at historically low levels amid worries about the global economy.

Mortgage buyer Freddie Mac says the average rate on a 30-year, fixed-rate mortgage remained at 3.65 percent this week after dropping for six straight weeks. The average rate on 15-year fixed-rate mortgages was also unchanged from last week at 2.95 percent after falling for five consecutive weeks.

The average rate on five-year adjustable rate mortgages blipped up to 2.85 percent this week from 2.83 percent last week.

Interest rates are still low two months after the Federal Reserve raised the short-term rate it controls for the first time since 2006. Worries about the global economy have coaxed investors into seeking the security of U.S. Treasurys. Their purchases have pushed down the yield on the benchmark 10-year Treasury note, which influences long-term mortgage rates, to 1.81 percent from 2.27 percent before the Fed hiked rates Dec. 16.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country at the beginning of each week. The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fees for 30-year and 15-year mortgages were unchanged at 0.5 point.

The fee on a five-year adjustable rate mortgage remained at 0.4 point.