Two L-3 Communications Holdings Inc. units were sued by ethnic Serbians who claim the company’s MPRI military consulting firm trained and equipped Croatian forces for mass killings during a 1995 offensive. The lawsuit against L-3 Communications Corp. and MPRI Inc. was filed yesterday at the federal courthouse in Chicago. The plaintiffs seek class-action…status on behalf of all Serbs residing in the Krajina region of Croatia that year. “Whether MPRI personnel took part in the genocide is not known and not alleged here,” according to the complaint. “What is known definitively is that MPRI provided the means that enabled the genocide to occur.”…L-3’s corporate communications department did not immediately reply to an e-mailed request for comment on the allegations contained in the complaint.