McLEAN, Va. -- Mortgage rates are up for the sixth time in as many weeks, to their highest level in nearly four years.

Freddie Mac said Thursday that 30-year, fixed-rate mortgages averaged 6.59 percent this week compared with last week's average of 6.58 percent.

Last year at this time, the 30-year rate averaged 5.75 percent.

A competing survey from Bankrate.com had 30-year, fixed-rate mortgages at 6.67 percent this week.

Frank Nothaft, Freddie Mac's chief economist, said that while mortgage rates will continue to rise over the coming year, the uptick "will be modest at best."

Even so, he predicted that the higher rates may keep some homeowners from refinancing their mortgage.

"Fewer families will be refinancing; but of those who are, a larger percentage will be drawing some equity out of their homes, many to pay off previously existing home-equity loans and lines of credit as these loans become more expensive," Nothaft predicted.

Freddie Mac said that rates on 15-year, fixed-rate mortgages, a popular choice for refinancing a home mortgage, also edged up this week to 6.22 percent, from 6.21 percent last week.