Vehicle sales this month are not getting a boost from government stimulus measures aimed at spurring demand for new, fuel-efficient cars, an industry group said.

May sales are so far showing a decline from last year's 221,377 vehicles, Satoshi Aoki, chairman of the Japan Automobile Manufacturers Association, said Thursday. Tax breaks implemented in April will likely boost sales later this year, he said.

"The effect of the tax breaks are starting to be reflected in customer orders, and this will lead to sales," Aoki said.

Japan is offering incentives to promote fuel-efficient vehicles and halt a 31 percent slide in auto demand through April. Electric, hybrid, natural gas, plug-in hybrid and some diesel vehicles now qualify for an exemption from weight and purchase taxes.

Nissan Motor Co. said this week that sales this month have risen 30 percent so far compared with last year as 14 of its models qualify for the tax break. Fuji Heavy Industries Ltd. President Ikuo Mori said Wednesday that auto sales may have "bottomed."

The reduced taxes are also applied to other vehicles that meet fuel-efficiency standards. Buyers can save as much as ¥137,700 on taxes on a "next-generation" car such as a hybrid, according to the auto group.