Mortgage applications shot up last week to the highest level since December, as low interest rates led to increased refinancing activity and a slowly improving jobs situation is starting to help the mortgage market, according to a leading trade association. The Mortgage Bankers Association said its market composite index rose 15.5% for the week ended March 4. On an unadjusted basis, the index climbed 16.1% last week. The prior week did not include an adjustment for the President’s Day holiday. “Taking into account typical seasonal patterns, purchase applications rose to their highest level of the year last week. On an unadjusted basis, purchase application activity is the highest since last May,” said Michael Fratantoni, MBA’s vice president of research and economics. “An improving job market is beginning to pave the way for an improving housing market. Additionally, mortgage interest rates remained below 5% for a second week, maintaining affordability for buyers and leading to an increase in refinance applications.” Refinancing activity rose 17.2% last week to the highest level since early January. The purchase index increased 12.5% from the week earlier to the highest level of 2011. The unadjusted purchase increased 14.3% from the prior week but is also 14.3% lower than a year earlier. In four-week moving averages, the market index is up 2.7%, with the purchase index 1.2% higher and the refinance index is up 3.6%. The level of refinancings rose last week but remains lower than it has been. The loans accounted for 65.5% of all mortgage applications last week up from 64.9% the prior week. The MBA said the average interest rate for a 30-year fixed mortgage increased to 4.93% last week from 4.84% the prior week. The average rate for a 15-year fixed mortgage stayed flat at 4.17%. Write to Jason Philyaw.