NEW YORK (CNN/Money) - Mortgage rates posted their biggest gains in four weeks thanks to stronger economic growth, Freddie Mac reported Thursday.

The rate on 30-year fixed-rate mortgages averaged 5.82 percent in the week ended Thursday, with an average 0.6 of a point payable up front, up from last week when it averaged 5.72 percent. It was the biggest increase since the week ended Sept. 9.

A year earlier, the rate on the 30-year fixed-rate loan stood at 5.77 percent.

The 15-year mortgage rate rose to 5.24 percent this week from 5.12 percent last week, also with 0.6 of a point up front. Last year, the average rate stood at 5.1 percent.

"The financial market thinks we've passed the 'soft patch' in the economy, which would translate into stronger growth in the coming months," Amy Crews Cutts, Freddie Mac deputy chief economist, said in a statement.

"Stronger growth means a greater threat of inflation and that means interest rates will start to rise in response to the threat."

One-year adjustable rate mortgages (ARMs) averaged 4.08 percent, up from 3.97 percent the week prior, with 0.6 of a point payable up front despite relatively low yields for the benchmark 10-year Treasury note, currently at 4.24 percent.

At this time last year, the average rate for ARMs was 3.72 percent.

"Today's rates are still a great bargain compared to even just a few years ago, when long-term mortgage rates astounded the industry by falling to about 7 percent and even lower," Crews Cutts adds.

"Better yet, our current forecast calls for rates to remain at low levels through the end of next year."

Mortgage rates have stayed relatively low despite rising rates elsewhere across the economy.

The Federal Reserve has raised its target for the federal funds rate, an overnight bank lending rate, three times this year to 1.75 percent.

And yields on 10-year Treasuries have stayed relatively low as well, though they have been rising in recent days.

Freddie Mac's average mortgage rates are based on a survey of 125 lenders nationwide.