Japan's producer price index (PPI) gained 4% on year in April and gained 0.2% from the month prior, the Bank of Japan reported on Wednesday.

The PPI saw a revised 4.3% on-year rise in March, data showed.

In April, the two biggest contributors to the index, namely beverages and foods, and transportation equipment, grew 3.6% and 1.6%, respectively, year on year, the central bank reported.

Fossil fuels prices were up 6.6% on year, electric power, gas, and water bills climbed 10.1%, while agriculture, forestry and fishery products prices surged 42.2%, according to the report.

The PPI measures prices at the factory gate, or those charged to businesses and distributors.

It is distinct from the consumer price index (CPI), which measures prices in retail locations. The PPI is considered a precursor to future movements in the CPI, as retailers try to recoup costs.