(Reuters) - Live Nation and its Ticketmaster unit have been hit with the first in a likely wave of new consumer antitrust lawsuits after the U.S. government and states sued to break up the two companies on Thursday.

The first consumer class-action lawsuit to piggyback on the government cases was filed later on Thursday in Manhattan federal court, seeking $5 billion in damages on behalf of potentially millions of ticket purchasers.

The cases accuse Live Nation of exerting monopoly control over the live events industry, threatening venues that work with rivals and boxing out competitors.

Consumer cases related to U.S. or state attorneys general lawsuits can pile up quickly and put added legal pressure on companies.

Lawyers for the class action plaintiffs at Robbins Geller Rudman & Dowd and Israel David did not immediately respond to requests for comment.

Live Nation on Thursday called the government lawsuit "baseless" and said there was "more competition than ever" in the live events market.

Lawyers who reviewed the government complaint said Live Nation could base its defense partly on the Justice Department's decision to sign off on Live Nation's Ticketmaster acquisition more than a decade ago.

Crowell & Moring's Eric Enson, an antitrust lawyer who is not involved in the lawsuit, said the government's case raised thorny "legal and factual questions about whether a breakup is a legally permissible remedy."

The case might resonate with consumers who have long complained about ticket prices, he said, "but proving antitrust cases to juries can be difficult."

However, antitrust legal scholar Rebecca Allensworth of Vanderbilt University said while the public's opinion of Live Nation is legally unimportant, "appearances matter in cases, maybe especially when they are decided by juries."

The Justice Department said the prior case involved a different antitrust law and that Live Nation had since shown "more expansive forms" of anticompetitive conduct.