Police arrested 58 flag-waving, slogan-chanting animal rights activists after they blocked traffic in a busy intersection and forced open a door at the National Institutes of Health.

"This is the first step in voicing your opinion and letting it be known that people are opposed to this kind of cruelty to animals," said Zakki Jewad, 25, of Silver Spring, Md.Organizers said the aim of the protest in this Washington, D.C., suburb was to kick off a week of civil disobedience and rallies at research centers and universities nationwide.

"We're protesting the murders of millions of animals in research laboratories every year," said Lee Warren, 61, of Baltimore, who came to Monday's rally toting a sign and dressed in a full-length black cape and hood to represent death.