China has initiated an antitrust investigation into Google, primarily targeting the Android operating system. This could be a strategic warning to Washington amidst ongoing trade tensions. The investigation is also focused on removing restrictions imposed on Chinese smartphone makers.

China said it was opening an antitrust probe into Google, part of a series of actions Tuesday that also included tariffs on U.S. coal and liquefied natural gas imports as well as restrictions on the export of certain metals.

China has announced a flurry of retaliatory measures against the U.S., including tariffs on imports of products such as coal, liquefied natural gas products and crude oil, as well as an antitrust probe into Google.