(Reuters) - Apple has been hit with a flurry of new consumer lawsuits accusing the iPhone maker of monopolizing the smartphone market, piggybacking on a sweeping antitrust case lodged by the U.S. Justice Department and 15 states last week.

At least three proposed class actions have been filed since Friday in California and New Jersey federal courts by iPhone owners who claim Apple inflated the cost of its products through anticompetitive conduct.

The lawsuits, seeking to represent millions of consumers, mirror the Justice Department's claims that Apple violated U.S. antitrust law by suppressing technology for messaging apps, digital wallets and other items that would have increased competition in the market for smartphones.

Apple has denied the government's allegations. The Cupertino, California-based company did not immediately respond to a request for comment on the consumer lawsuits.

Attorney Steve Berman, whose law firm Hagens Berman Sobol Shapiro filed one of the new cases, noted that his firm had earlier sued Apple for allegedly thwarting competition for its Apple Pay mobile wallet.

"We are pleased that the DOJ (Department of Justice) agrees with our approach," Berman said.