Wholesale prices rose 1.6 percent in July from a year earlier for the fifth straight monthly rise and the biggest gain in 13 years, the Bank of Japan said Wednesday in a preliminary report.

The prices, measured by the central bank's corporate goods price index, registered 96.4 against the base of 100 for 2000.

The margin of the gain in July was the largest since May 1991, indicating a rising trend in prices in corporate transactions has taken root.

The index rose 0.2 percent in March for the first rise since July 2000, and registered gains of 0.6 percent in April, 0.9 percent in May and 1.4 percent in June.

The CGPI is designed to show movements of the prices of goods traded among companies.

The rise in the overall wholesale prices in July stemmed mainly from surges in petroleum and coal product prices as crude oil prices soared in the global market, as well as rises in steel product prices due to strong demand from China, according to the BOJ.

Prices of petroleum and coal products surged 13 percent, while steel product prices jumped 14.3 percent.

Meanwhile, prices of electrical appliances dropped 4.2 percent, due to technical innovations and intensifying competition in such products as mobile phones and video cameras, the report says.

Export prices fell 2.3 percent from a year earlier in yen terms, but rose 2.3 percent in terms of contract currencies.

Import prices rose 4.9 percent in yen terms and 11.3 percent in terms of contract currencies.