A few arrests were reported.
Police said they were kept busy throughout the weekend with a steady stream of calls in the downtown area, including an attempted mugging, several small fires and a noisy confrontation with a pizza delivery person.
"Occupy Portland protesters became enraged when Pizza Schmizza ran out of bread sticks to accompany their order," the Portland Police Bureau said in a written update. "They threatened to assault employees and vandalize the restaurant."
The protesters' encampment is at Terry Schrunk Plaza, which police said was federal property and under the jurisdiction of the U.S. General Services Administration.
The (Portland) Oregonian said the occupiers had formed an ad hoc security team to prevent trouble but they required police assistance with various scuffles Sunday night. One protester raised the idea of electing a more-formal leadership for the camp, but the idea was shouted down at the group's daily public forum.
In Atlanta, five people were arrested, including a woman draped in an American flag, after refusing to leave Woodruff Park in the city's downtown area, The Atlanta Journal Constitution reported.
The Los Angeles Times said 11 Occupy Riverside (Calif.) participants were hauled away for refusing to strike their tents.
Protesters in Honolulu asked for donations to recover $1,700 in bail money after eight people were arrested during a sit-in at one of the city's oldest community parks Saturday.
"We are asking support from the community to help raise bail money to pay back those who cannot afford to pay," the Occupy group said on its Web site.