WASHINGTON — Mortgage rates shot up this week, with 30-year mortgages climbing to the highest level in nearly a year, reflecting concerns in financial markets about the troubles at mortgage giants Fannie Mae and Freddie Mac.

Freddie Mac reported yesterday that in its nationwide survey rates on 30-year mortgages surged to 6.63 percent this week, up sharply from 6.26 percent last week. That's the highest since last August.

Other mortgage rates showed similar hefty increases, which analysts attribute to financial market jitters over rising mortgage losses at Fannie and Freddie, which together either own or guarantee nearly half of the nation's mortgages.

Rates on 15-year fixed-rate mortgages, a popular option for refinancing, rose to 6.18 percent, up from 5.78 percent last week.

Five-year adjustable-rate mortgages rose to 6.16 percent, up from 5.80 percent. Rates on one-year ARMs jumped to 5.49 percent, from 5.10 percent.

The House on Wednesday approved legislation to help shore up Fannie and Freddie finances and stock if necessary.