NEW YORK (CNN/Money) - Mortgage rates climbed in the latest week, but the recent increase failed to dampen activity in the sizzling housing market, an economist said Thursday.

The 30-year mortgage rate rose to 6.28 percent in the week ending Aug. 22 from 6.24 percent a week earlier, with an average of 0.8 of a point payable up front, mortgage lender Freddie Mac reported Thursday. The 30-year stood at 6.27 percent a year ago.

The 15-year fixed-rate mortgage climbed to 5.60 percent, with 0.8 of a point up front, up from 5.58 percent and below the 5.71 percent level of a year ago.

And the rate on one-year adjustable-rate mortgages (ARMs), loosely indexed to the 10-year Treasury note, rose to 3.84 percent, with 0.7 point up front, from 3.75 percent last week. At the same time last year, the one-year ARM averaged 4.34 percent.

"The recent upswing in mortgage rates does not seem to have slowed the new home construction market, if July's housing starts figures are any indication," said Frank Nothaft, Freddie Mac chief economist. "Total starts hit a 17-year high in July while single-family starts in the same month were at the highest level since 1978.

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"Even as mortgage rates continued to climb in August, builder confidence reached its highest level in three and one half years, according to the National Association of Home Builders. This would seem to indicate that 2003 will continue to be an outstanding year for the housing industry."

Freddie Mac's average mortgage rates are based on a survey of 125 lenders nationwide. The rates include those on mortgages accepted by borrowers with good credit ratings who place a 20 percent down payment on their homes, according to Freddie Mac. The total amount of each mortgage considered for the survey doesn't exceed a $322,700 limit.

CNNfn's Lisa Leiter takes a closer look at the increasing concern over rising mortgage rates. Play video (Real or Windows Media)

Freddie Mac (FRE: up $0.30 to $50.70, 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.

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