Wholesale prices fell 2.1 percent in July from a year earlier for the fourth straight month of decline amid weaker crude oil prices, the Bank of Japan said Friday.

The year-on-year rate of decline was the largest since January 2010. The index of corporate goods prices stood at 100.1 against the 2010 base of 100, the central bank said in a preliminary report.

On a month-on-month basis, the index was down 0.4 percent from June.

By product, prices of petroleum and coal products as well as prices of iron and steel lost 8.5 percent each. A BOJ official said that iron and steel prices are dropping partly because cheaper products are being imported.

Prices of information and communications equipment, an area of tough price competition in the domestic market, meanwhile fell 9.1 percent.

As for the outlook, the official said that, while crude oil prices have risen in July and August so far, strong uncertainties over the prospects of overseas economies may weigh on the index.

Japan's export prices declined 4.1 percent from a year earlier in terms of the yen and fell 2.7 percent on a contract currency basis.

Import prices decreased 5.5 percent in yen terms, the largest rate of decline since November 2009, and 4.8 percent on a contract currency basis.