NEW YORK, JAN. 23 -- Super-strict security is in force after gay rights activists tried to disrupt Tuesday night's broadcasts of the "CBS Evening News" and PBS's "MacNeil/Lehrer NewsHour" with chants of "Fight AIDS, not Arabs."

Using fake identification cards, the demonstrators from the group ACT-UP walked past security guards and penetrated newsrooms at both networks. Four others attempted a similar strike at NBC but were apprehended on the third floor at Rockefeller Center before they reached the set of Tom Brokaw's "Nightly News."

All the demonstrators, three at CBS and seven at WNET-TV, where "NewsHour" originates, were arrested and removed after the brief disruptions.

Security at all the New York-based networks was beefed up virtually to theater-of-war levels today, and no one would discuss the matter.

CBS spokesman Tom Goodman reflected the growing tension when a reporter asked permission to visit news division headquarters for a close-up look at security precautions.

"Doing a story on how a company secures itself gives any human being with a warped mind an idea of how to get around it," he said. "Anything you report on our security would endanger the security of individuals.

"Even to come down here and have a cup of coffee and chat, you'd leave here knowing what our security system is, with the ability to report it," Goodman said. "I don't think that would be a responsible thing for any media organization to do. You won't get past the front door."

At the "MacNeil/Lehrer NewsHour," Executive Producer Les Crystal said the incident was the first in his experience, and while denying it had resulted in "a bunker mentality," he too declined to describe increased security measures.