WASHINGTON (AP) — Average long-term U.S. mortgage rates fell this week for a fourth straight week amid persisting turmoil in stock markets and global economic worries.

Mortgage buyer Freddie Mac said Thursday the average rate on a 30-year fixed-rate mortgage slipped to 3.79 percent from 3.81 percent a week earlier. That means it stays below the symbolically significant 4 percent level. The rate has increased from its 3.66 percent average a year ago but remains well below its historic average of 6 percent.

The average rate on 15-year fixed-rate mortgages declined to 3.07 percent from 3.10 percent.

The Federal Reserve sounded a note of concern Wednesday about how global pressures could affect a slowing U.S. economy. Fed policymakers kept a key interest rate unchanged following their meeting this week.

The continuing volatility in global stock markets has pushed up prices of U.S. government bonds as investors seek safety. That has depressed the yields on the bonds, which mortgage rates track.

The yield on the 10-year Treasury bond stood at 2 percent Wednesday, after dropping to 1.98 percent a week earlier — its lowest level since October. The yield was stable at 2 percent Thursday morning.

The benchmark yield has fallen sharply since the start of the year amid the market turbulence. At the end of 2015, it was 2.30 percent.

The sustained decline in mortgage rates in recent weeks has spurred prospective homebuyers. Applications for mortgages increased 8.8 percent in the week ended Jan. 22 from the previous week, according to the Mortgage Bankers Association.

The number of people signing contracts to purchase homes managed to inch up last month, thanks to unseasonably warm weather in the Northeast, data issued Thursday by the National Association of Realtors showed. The tiny bump suggests that home sales may plateau this year after a solid increase in 2015.

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 fee for a 30-year mortgage was unchanged from last week at 0.6 point. The fee for a 15-year loan remained at 0.5 point.

The average rate on five-year adjustable-rate mortgages slipped to 2.90 percent from 2.91 percent; the fee stayed at 0.5 point.