The back and forth goes on in the US Federal Trade Commission's antitrust suit against Qualcomm, the world's largest maker of mobile chips.

Late Friday night, Qualcomm fired the latest salvo in the case, filing documents in which it says, for a second time, that the FTC's suit should be dismissed because it doesn't back up the agency's claims that Qualcomm's practices hampered competition.

The FTC filed its suit in January, saying Qualcomm imposed "onerous" supply and patent-licensing terms to extract high royalties from cell phone manufacturers and weaken rivals. In April, Qualcomm responded, saying the case didn't hold water and should be dismissed. That prompted the FTC to file papers last month defending its suit and saying the case should go forward. And that's what brought on Friday's filing.

"We note in our reply brief...that the FTC cannot and has not adequately defended its defective complaint," Don Rosenberg, executive vice president and general counsel for Qualcomm, said in a statement. "The complaint lacks necessary facts and fails to plead a coherent theory of competitive harm. Improperly adding alleged 'facts' supplied by competitors' briefs cannot prop up a deficient complaint." Qualcomm rivals Samsung and Intel had earlier filed friend-of-the-court briefs in support of the FTC's case.

The FTC didn't immediately respond to a request for comment on Qualcomm's latest filing.

The lawsuit continues a pattern of antitrust scrutiny directed at Qualcomm in recent years. In December, the South Korean Fair Trade Commission hit the chipset maker with an $850 million fine for maintaining an "unfair business model" and creating a monopoly with its practices. In February, China fined Qualcomm almost $1 billion as part of a long-running antimonopoly investigation into the company.

CNET's Steven Musil contributed to this report.