WASHINGTON, March 21 (Xinhua) -- The U.S. Justice Department, along with 16 other state and district attorneys general, on Thursday filed a civil antitrust lawsuit against Apple, accusing the tech giant of illegally maintaining a monopoly over smartphones.

"Apple has maintained monopoly power in the smartphone market not simply by staying ahead of the competition on the merits, but by violating federal antitrust law," Attorney General Merrick Garland said at a press conference in Washington, D.C.

"We allege that Apple has employed a strategy that relies on exclusionary, anticompetitive conduct that hurts both consumers and developers," said Garland. "Consumers should not have to pay higher prices because companies break the law."

The attorney general said Apple carries out its exclusionary, anticompetitive conduct in two principal ways: First, Apple imposes contractual restrictions and fees that limit the features and functionality that developers can offer iPhone users.

Second, Apple selectively restricts access to the points of connection between third-party apps and the iPhone's operating system, degrading the functionality of non-Apple apps and accessories.

Additionally, iPhone users perceive rival smartphones as being lower quality because the experience of messaging friends and family who do not own iPhones is worse -- "even though Apple is the one responsible for breaking cross-platform messaging," he said.

Apple has justified its practice of regulating downloads through the App Store, arguing that it is essential for maintaining the iPhone's security by minimizing the risk of viruses and fraudulent activities.

Tech giants have been facing growing scrutiny in recent years. After a 16-month investigation into Apple, Amazon, Facebook (now Meta) and Google, the antitrust subcommittee under the House Judiciary Committee released a report in October 2020, arguing that the four Big Tech companies enjoy monopoly power and need more government regulation.

The lawsuit against Apple marks the latest action taken by U.S. antitrust authorities against the "Big Four". Antitrust regulators have also filed antimonopoly lawsuits against the other three.