Japan Post Co. is considering a hike in the parcel delivery fees it charges large clients due to a surge in online shopping packages and manpower shortages, industry sources said on Wednesday.

Earlier this week it was also reported that Yamato Holdings Co., the biggest parcel delivery company in the country, was asking major online retailers such as Amazon.com Inc. to pay higher shipping fees.

Yamato's fee hike could prompt its clients to seek better rates from other delivery companies for some or all of their business, creating opportunities for other delivery service providers.

Yamato has a 47 percent share of the nation's parcel delivery market while Japan Post has a 14 percent share.

Online retailers typically negotiate steep discounts off the regular shipping fees set by delivery companies, an industry source said.