Japan's wholesale price inflation jumped in May, due to both the rising cost of electricity and the weak yen.

The Bank of Japan says the preliminary Producer Price Index for the month was up 2.4 percent from a year earlier.

That's a sharp increase compared to the 1.1 percent marked in April. The figure hit the 2-percent level for the first time in eight months.

The index measures the prices companies charge each other for goods and services.

A surcharge that's added to electric bills to cover the cost of renewable energy was raised last month. This was the main factor behind the rise in producer prices.

Looking ahead, electric bills are also rising due to the end of government energy subsidies. Import prices remain high due to the weak yen.

The focus now is on how these factors and a move to pass on higher labor costs through price increases will affect the index in future.