NEW YORK (CNN/Money) - Mortgage rates continued their run off record lows as resolution on the United States' course of action led some investors to turn a focus to the long-term economic picture, Freddie Mac said Thursday.

The 30-year mortgage averaged 5.91 percent for the week ending March 28, with an average of 0.6 of a point payable up front to the lender; that's up slightly from a record low of 5.79 percent last week, according to the lender.

Last year at this time, the long-term mortgage rate stood at 7.18 percent.

The 15-year fixed-rate mortgage also rose, averaging 5.21 percent, with 0.6 of a point payable up front, up from 5.11 percent last week. The 15-year rate averaged 6.6 percent one year ago.

One-year adjustable-rate mortgages (ARMs), loosely indexed to the 10-year Treasury note, averaged 3.84 percent, up from 3.75 percent a week ago. The one-year average stood at 5.11 percent for the same week last year.

"Following the onset of the Iraqi conflict, financial markets seem to have an upward bias for mortgage rates," said Frank Nothaft, Freddie Mac chief economist. "However, that's not to say that uncertainty has diminished in any large way, but that it has shifted to a different set of unknowns."

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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 $300,700 limit.

Freddie Mac (FRE: up $0.32 to $53.42, 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.