Washington -- The FBI has collected extensive information on the tactics, training and organization of antiwar demonstrators and has advised local law enforcement officials to report any suspicious activity at protests to its counterterrorism squads, according to interviews and a confidential bureau memorandum.

The memorandum, which the bureau sent to local law enforcement agencies last month in advance of antiwar demonstrations in Washington and San Francisco, detailed how protesters have sometimes used "training camps" to rehearse for demonstrations, the Internet to raise money, and gas masks to defend against tear gas. The memorandum analyzed lawful activities such as recruiting demonstrators, as well as illegal activities such as using fake documentation to get into a secured site.

FBI officials said in interviews that the intelligence-gathering effort was aimed at identifying anarchists and "extremist elements" plotting violence, not at monitoring the political speech of law-abiding protesters...