U.S. fixed mortgage rates edged down slightly this week and remained near historic lows, according to the Primary Mortgage Market Survey released by Freddie Mac Thursday.

The mortgage giant said the 30-year fixed-rate mortgage (FRM) fell to 3.54 percent in the week ending April 4, down from 3.57 percent in the previous week.

The 15-year FRM, a popular choice for those looking to refinance, dipped to 2.74 percent from 2.76 percent in the previous week.

Both were elevated from the record lows of 3.31 percent and 2. 63 percent respectively. Since the beginning of this year, U.S. fixed mortgage rates have maintained a modest upward trend as the housing market bottoms out. But rates remained at an affordable level for house buying and refinancing.

In addition, the five-year Treasury-indexed hybrid adjustable- rate mortgage (ARM) went down to 2.65 percent, while the one-year Treasury-indexed ARM rose to 2.63 percent.

"Fixed mortgage rates dipped slightly while the manufacturing industry showed signs of slowing," said Frank Nothaft, vice president and chief economist of Freddie Mac.

The U.S. Institute of Supply Management (ISM) said Monday the manufacturing index, also known as the purchasing managers index ( PMI), edged down from the revised reading of 54.2 percent in February to 51.3 in March, signaling slower pace of growth.