WASHINGTON, Oct. 20 (Xinhua) -- U.S. Justice Department on Tuesday filed an antitrust lawsuit alleging Google of "unlawfully maintaining monopolies" in the search and search advertising markets, the department said in a statement.

The lawsuit was filed against the California-headquartered company in the U.S. District Court for the District of Columbia. Eleven state attorneys general joined the department as plaintiffs in the case.

As one of the wealthiest companies on the planet with a market value of 1 trillion U.S. dollars, Google, owned by Alphabet Inc., is the "monopoly gatekeeper to the Internet" for billions of users and countless advertisers worldwide, the department said.

For years, Google has accounted for almost 90 percent of all search queries in the United States and has "used anticompetitive tactics to maintain and extend its monopolies in search and search advertising," it continued.

The Complaint alleges that Google has unlawfully maintained monopolies in search and search advertising by entering into exclusivity agreements that forbid preinstallation of any competing search service, and entering into long-term agreements with Apple that require Google to be the default.

The tech giant also allegedly used monopoly profits to buy preferential treatment for its search engine on devices, web browsers, and other search access points, "creating a continuous and self-reinforcing cycle of monopolization," according to the department.

"Today, millions of Americans rely on the Internet and online platforms for their daily lives. Competition in this industry is vitally important, which is why today's challenge against Google -- the gatekeeper of the Internet -- for violating antitrust laws is a monumental case both for the Department of Justice and for the American people," said Attorney General William Barr.

A Google spokesperson, meanwhile, was cited by CNBC as saying that the lawsuit is "deeply flawed," arguing that people use Google because they choose to -- not because they're forced to or because they have no other choices.