The Japanese Fair Trade Commission has conducted an inspection on the offices of Amazon over allegations that it compelled vendors to favour its website over competitors.
The anti-monopoly watchdog agency conducted the raids recently over suspicions that the online retailer could have asked vendors to reduce prices of their products than for rival sites, reported Nikkei Business Review, citing sources.
According to the country's anti-monopoly act, companies are barred from unfairly resorting to practices that restrict the activities of business partners.
The US is the largest market for Amazon, followed by Germany, the UK and Japan.
In the 2015 fiscal year, the Japanese unit of Amazon sold roughly $8.3bn, accounting for approximately 7% of the company’s total net sales of $107bn worldwide.
Its key competitor in Japan, Rakuten, posted online revenues of $2.9bn during this period.
Amazon's business practices with its vendors have also come under investigation in Europe.
Last November, Germany launched a probe into Apple and Amazon following complaints that audiobook publishers were compelled to accept 'unreasonable conditions'.