The Terrorism Research Center, an Arlington, Va., group, said one site posted more than 50 photographs of the destruction. Another compiled news clips into a propaganda video, while an unnamed writer on another claimed "Katrina is the newest soldier of God."
Terrorists are monitoring the much-criticized federal response to Hurricane Katrina, as are lawmakers and homeland security experts.
Katrina's aftermath "has grave implications for our ability to deal with terrorism," said Rep. Jane Harman of California, the House Intelligence Committee's top Democrat.
"I couldn't help but think how much this resembles the detonation of a weapon of mass destruction in a major American city. ... I have no doubt the terrorists have watched this unfold and they understand its implications," Harman said.
Experts say Katrina should be carefully and critically examined for its broader implications to terrorism.
"We need to move past the finger-pointing and really try to take Katrina as a case study to distill some lessons learned from it," said terrorism expert Brian Jenkins, senior adviser to the president of RAND Corp., a national security think tank.
Jenkins said the problems encountered in getting residents out of New Orleans should prompt questions about how well other cities can be evacuated. Depending on the type of incident, he said, officials may need to mobilize more ways to get people out or to encourage them to stay put and "shelter in place" if that can be done safely.
Jenkins said the disturbing images of dead bodies, flood-ravaged towns and pleading victims also point to the need to address the psychological effects of disasters, including panic. "Terrorism is not simply what the terrorists can do, but the terror created by those events," he said.