OAKLAND, Calif. — Protesters and city officials here took a deep breath and tried to calm the waters Thursday after a night of vandalism and tear gas disrupted an orderly day of anti-Wall Street marches. But tensions remained high, both between demonstrators and the police and between Occupy Oakland protesters and a belligerent fringe group that seemed intent on clashing with law enforcement and destroying property.

More than 100 people were arrested in the melee, and the injured included both protesters and police officers.

After an afternoon of picketing banks, a crowd that city officials estimated as at least 7,000 strong descended on the city’s waterfront Wednesday evening, temporarily closing one of the busiest ports in the country. Port officials reported no injuries or property damage, and the port was reopened Thursday morning.

Meanwhile, several hundred protesters regrouped near the Occupy Oakland encampment downtown. Shortly before midnight, some of them entered a nearby abandoned building. Objects were hurled at police officers, who then declared the crowd an unlawful assembly and began firing tear gas and beanbag projectiles.