U.S. 30-year fixed mortgage rates increased to 3.71 percent, reversing six weeks of declines after modestly positive economic data, mortgage financier Freddie Mac said Thursday.

The 30-year rate rose from 3.67 percent in the prior week, but far below the previous year's rate of 4.5 percent. Fifteen-year fixed-rate mortgages rose to 2.98 percent from 2.94 percent in the previous week. Five-year Treasury-indexed hybrid adjustable-rate mortgages, or ARMs, fell to 2.80 percent from 2.84 percent in the previous week. One-year ARMs were down slightly to 2.78 percent from 2.79 percent in the previous week.

Fixed mortgage rates edged up slightly from record lows during a mild week of economic data releases, said Frank Nothaft, Freddie Mac's chief economist, citing the Federal Reserve board's report that household net worth rose by $2 trillion to $62.9 trillion in the first quarter, due to gains in stock markets.