Mortgage rates fell over the past week, sending the 15-year benchmark to a record low, mortgage giant Freddie Mac said Thursday.

While 30-year fixed-rate mortgages are more common, low mortgage rates have made 15-year notes more realistic for some homeowners, especially those who have relatively low balances and want to pay off their principal more quickly.

The average 15-year rate for mortgage deals done over the past week was 3.11 percent, down from 3.13 percent a week ago. Monthly principal and interest payments on a $200,000 mortgage at that rate would be about $1,392.

Meanwhile the average 30-year rate fell last week to 3.88 percent from 3.98 percent. That would equate to an average monthly payment of $941 on the same $200,000 mortgage. Payments are lower on the longer-term mortgage, but interest paid over the life of the loan is far higher.

Rates fell for a third straight week in part because of last Friday's weak monthly employment report, said Frank Nothaft, chief economist for Freddie Mac.

"On a more positive note, the Federal Reserve reported hiring was steady, or showed a modest increase, across many of its districts in its April 11 Beige Book of regional economic conditions," Nothaft said.