Wholesale prices rose 3.3 percent in May from a year earlier, their strongest year-on-year rise since March 1981, during the second oil crisis, the Bank of Japan said Monday.

The BOJ's corporate goods price index came to 100.6 against a base of 100 for 2000, the central bank said in a preliminary report.

Behind the spike was a strong increase in prices for crude oil and other commodities, on the back of growing demand in emerging economies, particularly in China and India, BOJ officials said.

It is the first time the index has topped 100 since August 2000. The index also posted its 27th consecutive year-on-year increase.

Petroleum and coal product prices surged 20.6 percent in May from a year earlier, while those of nonferrous materials jumped 63.4 percent.

The effect of price rises in the corporate sector has been gradually spilling over into the household sector as, for example, major paper companies recently announced plans to raise prices for tissue paper.

In contrast, prices of electrical machinery and equipment fell 2.4 percent, due mainly to lower prices for mobile phones, the BOJ officials said.

Wholesale prices rose 0.7 percent from April.

Import prices jumped 15.4 percent from the year before in yen terms and 11.4 percent in terms of contract currencies.