Average interest rates for conventional 30-year, fixed-rate mortgage loans of $417,000 or less rose one basis point to reach 4.88% in May, the U.S. Federal Housing Finance Agency said Thursday.

Meanwhile, average interest rates on 15-year fixed-rate loans of $417,000 or less fell four basis points to 4.71% in the month.

The figures reflect loans that closed between May 22 and May 31. The changes come as initial fees and charges related to the loans rose slightly to equal 0.58% of a loan's balance in May.

The average loan amount rose $4,200 in May to $221,200.

The data are derived from a monthly survey conducted by the agency, which oversees Fannie Mae (FNM), Freddie Mac (FRE) and the nation's 12 Federal Home Loan Banks.

   
-By Meena Thiruvengadam, Dow Jones Newswires; 202-862-6629; meena.thiruvengadam@dowjones.com