If you've marched against the Iraq war or flashed a peace sign during a rally, the Pentagon may be keeping an eye on you. The U.S. military has been building a secret database that suggests it is monitoring peace demonstrations and collecting information on Americans who oppose the Iraq war.

The revelation was included in an "NBC Nightly News" report on Tuesday, which stated that a database obtained by the network included a list of 1,500 "suspicious incidents" across the U.S. over a 10-month period that included four dozen anti-war meetings or protests, some aimed at military recruiting.

The report referred to what it called a secret briefing document, which concluded: "We have noted increased communication between protest groups using the Internet," but not a "significant connection" between incidents. The documents were described as a peek at how the Pentagon has increased the pace of intelligence collection in the United States since the September 11, 2001 attacks.

A Pentagon spokesman declined to comment on the NBC report, saying "The Department of Defense uses counterintelligence and law enforcement information properly collected by law enforcement agencies. ... The use of this information is subject to strict limitations, particularly the information must be related to missions relating to protection of DoD installations, interests and personnel."

The Pentagon had previously acknowledged the existence of a domestic counterintelligence program known as the Threat and Local Observation Notice (TALON) reporting system. That system is designed to gather "non-validated threat information and security anomalies indicative of possible terrorist pre-attack activity."

The collection of information on Iraq war protests is reminiscent of similar activity during the Vietnam War era, when it was discovered that the Pentagon spied on anti-war and civil-rights groups and individuals. As a result, Congress held hearings in the 1970s in which it recommended strict limits on military spying inside the U.S.