Six Asian-American Syracuse University students have sued Denny's Inc., saying they were denied service at one of the chain's restaurants, shoved out by two security guards, and then beaten up by a mob of white customers as the Denny's guards stood by. Three black students, who said the guards threatened them with Mace when they aided the Asian-Americans, and a white student who accompanied the Asian-Americans also joined the suit. Two of the Asians were knocked unconscious during the April melee in Syracuse, the suit said. Attorney Elizabeth OuYang and several plaintiffs charged Thursday that Denny's had failed to make sure all its employees _ including those in Syracuse _ underwent anti-discrimination training as required by Denny's 1994 settlement of a class-action lawsuit. Denny's spokeswoman Karen Randall said the company was outraged by the incident and was firing some employees and disciplining others as a result. Denny's president John Romandetti expressed "deep regret" in a statement Thursday. The suit was filed in federal court in Syracuse and seeks unspecified damages. The suit says the students waited 30 minutes for tables while groups of white patrons were routinely seated, and after they complained they were forcibly ejected by two sheriff's deputies moonlighting as security guards. In the parking lot, the suit says, the Asian-American and black students had a shoving confrontation with the uniformed, armed guards, and then were jeered, racially insulted and physically attacked by 10 or more white youths who came out of the restaurant. Yoshika Kusada of Mahwah, N.J., broke down in tears as she recalled the incident. "It may be naive to ask for an end to racism . . . but this is for real and if allowed to continue we are all in danger," she sobbed. _ Information from the Associated Press and Bloomberg News was used in this report.