NEW YORK (CNN/Money) - Rates for long-term mortgages rose slightly this week as lower levels of mortgage applications for home purchases slowed, mortgage lender Freddie Mac said Thursday.

Freddie Mac reported that the 30-year mortgage averaged 6.27 percent in the week ending Aug. 23, with an average of 0.7 of a point payable up front to the lender. The rate rose slightly from an average 6.22 percent last week and remained lower than its average 6.91 percent a year ago.

The 15-year fixed-rate mortgage averaged 5.71 percent, up from 5.63 percent last week and down from 6.47 percent a year ago. The 15-year rate averaged 0.7 of a point payable up front.

One-year adjustable-rate mortgages indexed to the Treasury averaged 4.34 percent, with an average 0.7 of a point due up front, down slightly from 4.39 percent last week and down from an average of 5.68 percent a year ago.

"Both existing home sales in June and housing starts in July took a breather, dropping to somewhat more sustainable levels of activity," Freddie Mac chief economist Frank Nothaft said. "More recently, mortgage applications for home purchases in August indicate that the housing industry may finally be slowing to a still healthy, more normal pace." (Read more about increasing the resale value of a home.)

Freddie Mac (FRE: down $1.06 to $63.09, Research, Estimates), or Federal Home Loan Mortgage Corp., is a publicly traded company the government established in 1970 to provide a flow of funds to mortgage lenders. It buys mortgages from banks, bundles them and then resells them as mortgage-backed securities.

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Its products, and the products of other similar entities, have become increasingly popular as an alternative to government-backed bonds, particularly with international investors.