Japan's competition watchdog said Monday it has started investigating whether Google violated rules by asking smartphone manufacturers for preferential treatment, following similar steps by authorities in Europe and other major economies.

The Japan Fair Trade Commission probe adds to the search engine giant's other competition woes, including in the United States.

The Japanese agency said Google is suspected of inappropriately seeking to have its search apps be included in devices, with their icons in specific places.

Google also allegedly signed contracts with Android device makers not to include rival search apps in their products in exchange for sharing profits generated from advertisement revenues driven from Google searches, the agency said.

The commission will seek the public's input until Nov. 22.

Saiko Nakajima, head of the digital platform investigation division of the commission, said it became "difficult for other competitors to compete, no matter how much they try" when a powerful player like Google builds systems to maintain its influence.

"In the medium to long term, such a practice could stifle innovation in the field and consumers could become the ones to face disadvantages as a result," she said.

Google's Japan office said the company offers Android users "a choice to customize their devices to suit their needs, including the way they browse and search the internet, or download apps."

"We have continued to work closely with government agencies to demonstrate how we are supporting the Android ecosystem and expanding user choice in Japan. We will continue to collaborate with the government and industry partners throughout this process," it said.

Google is facing prosecution by the U.S. Justice Department because it illegally used its dominant position in online search to prevent the emergence of rivals.

At the heart of the case is Google's relationship with Apple and the special deals between the two behemoths that make the search engine the default on Apple's Safari browser.