MORTGAGES guaranteed by the Department of Veterans Affairs surged by 50 percent in the fiscal year ended Sept. 30, as tighter credit standards on conventional financing made these programs all the more attractive to current and former military members.

The department guaranteed almost 540,000 loans in fiscal year 2012, the most since 1994, according to Mike Frueh, the director of loan guarantee service. Compared with five years ago, volume is up some 300 percent.

Low interest rates were part of the draw — about 338,000 of the V.A. loans were for the purpose of refinancing.

Borrowers who already have a V.A.-backed mortgage can get an interest-rate reduction relatively easily. The department’s streamlined refinance program doesn’t require these borrowers to “re-prove” that they qualify, said Nathan Long, the chief executive of Veterans United Home Loans, an online broker of V.A. loans.