Fixed mortgage rates fell slightly for the week ending March 1, keeping interest rates near their 60-year lows, Freddie Mac said Thursday.

Freddie's Private Mortgage Market Survey shows the 30-year, fixed-rate mortgage averaging 3.90% for the week, which is down from 3.95% the previous week and 4.87% a year ago.

In addition, the 15-year FRM hit 3.17%, down from 3.19% a week earlier and 4.15% a year ago. 

Meanwhile, the 5-year Treasury-indexed hybrid adjustable-rate mortgage averaged 2.83% this week, up from 2.80% the week before and 3.72% a year ago.

The one-year Treasury-indexed ARM hit 2.72%, down from 2.73% a week earlier and 3.23% last year.

"Fixed mortgage rates bottomed out in January and February of this year which is helping spur the housing market," Frank Nothaft, vice president and chief economist with Freddie Mac.

He added, "For instance, pending existing home sales rose in January to its strongest pace since April 2010 and sales figures for December saw upward revisions. In addition, the Federal Reserve noted in its February 29th regional economic review (or Beige Book) that residential real estate activity increased modestly in most of its Districts over the course of January and early February, with several reports of increased home sales."