NEW YORK (CNNMoney.com) - Fewer people applied for mortgages in the U.S. for the second week in a row, an industry trade group said on Wednesday.

The Mortgage Bankers Association said its seasonally adjusted index of mortgage application activity for the week ended April 14 decreased 1.7 percent to 569.6 from the previous week's 579.4.

Fewer people applied for mortgages in the U.S. for the second week.

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Borrowing costs on 30-year fixed-rate mortgages, excluding fees, averaged 6.56 percent, up 0.06 percentage points from the previous week, its highest level in almost 4 years.

The MBA's seasonally adjusted purchase mortgage index fell 2.7 percent to 407.4 from the previous week's 417.7. The index is considered a reliable gauge of U.S. home sales.

The trade group's seasonally adjusted index of refinancing applications fell 0.4 percent to 1526.1 from 1532.4 in the previous week.

The refinance share of mortgage activity increased to 36.4 percent of total applications, from 36.0 percent last week.

The percentage of adjustable-rate mortgage activity rose to 28.9 percent of applications, from 28.6 percent prior.

Low mortgage rates have been behind a major U.S. housing boom over the last five years.

Fixed 15-year mortgage rates increased to 6.19 percent from 6.17 percent. Rates on one-year adjustable-rate mortgages increased to 6.00 percent from 5.97 percent.

The MBA's survey covers about 50 percent of residential mortgage bankers and thrifts.

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