The number of condominiums offered for sale in Tokyo and surrounding areas in May surged 49 percent, the biggest gain in more than a year, as the economy started to show signs of improvement.

Developers put 4,967 apartments on the market in May, compared with 3,329 units a year earlier, the Real Estate Economic Research Institute Co. said in a report released in Tokyo on Monday. The last time the monthly data had a bigger gain was April 2012, when it rose 82 percent.

More apartments are being offered on the market to capture potential buyers as Japan accelerates efforts under Prime Minister Shinzo Abe to end deflation and boost the world's third-largest economy. The supply of new apartments in Tokyo this year will reach the highest level since 2007 on the back of the economic recovery, according to an estimate by the institute.

Gross domestic product expanded an annualized 4.1 percent in the first quarter, compared with a preliminary calculation of 3.5 percent, the Cabinet Office said last week. Nominal GDP, which is unadjusted for changes in prices, rose 0.6 percent from the previous three months, leaving the economy 7 percent smaller than in the same period in 1997. Consumer confidence in May was at its highest level since 2007, a Cabinet Office survey showed.

The number of new apartments put on the market will rise 9.6 percent to about 50,000 units in 2013, according the Tokyo-based industry researcher. The institute had a forecast of 4,000 units for the month of May.

The Topix Real Estate Index, a measure of 43 property-related stocks, fell 1.5 percent as of 1:25 p.m. in Tokyo, paring an earlier loss of as much as 3.1 percent.