The protesters, who began tonight's rally at around 4 p.m., dispersed after the gas was released and it was not immediately clear if they would regroup tonight or continue to march.
The "Occupy Oakland" demonstrators announced earlier that they would return to the plaza every night at 6 p.m. to continue the protest.
Police used tear gas on protesters earlier tonight at around 7 p.m., temporarily scattering the crowd. A short time later the group reconvened at the plaza.
Police said that as of 8 p.m., no injuries had been reported.
BART closed Oakland's 12th Street station because of tonight's protest.
Protesters were ordered to leave the City Hall area for the first time at around 6 p.m. this evening and the crowd complied. The group briefly gathered at Snow Park, the smaller of two encampment sites that were broken up by police early this morning.
Police presence was less prevalent at the smaller park and after a brief discussion, the group decided to continue the march and return to 14th Street and Broadway.
Officers at Frank Ogawa Plaza again ordered the crowd to disperse before deploying tear gas and smoke grenades.
After fleeing briefly, the group gathered near 19th Street and Broadway, before heading back to City Hall.
Between 400 and 500 "Occupy Oakland" protesters began the march today at around 5:20 p.m. at the main branch of the Oakland Public Library heading to Frank Ogawa Plaza with the aim of retaking the space they were evicted from early this morning.
The protesters gathered outside the main branch of the library late this afternoon and vowed that Occupy Oakland protests will continue despite the arrest of a large group of people at an encampment outside City Hall this morning.
Veteran activist Krystof Lopaur of No Justice No BART told the gathering on the steps of the library, which is located on 14th Street between Oak and Madison streets, that the plan was to start marching to Frank Ogawa Plaza, the site of the encampment.
At around 5:20 p.m., the crowd began to make its way downtown.
"We're going to reclaim what was already ours," Lopaur said, drawing loud cheers from the crowd.
A large group of demonstrators stopped to rally near a police station at Seventh and Washington streets at around 6 p.m. Confrontations broke out between officers and protesters and the police deployed smoke grenades, which caused loud noises and filled the area with smoke.
Shortly before that confrontation, small skirmishes broke out near Eighth and Washington streets. Some protesters threw paint on the officers and minor altercations occurred. At least two protesters were detained during that confrontation.
Oakland police, as well as the Santa Clara County and Alameda County sheriff's departments and the California Highway Patrol, are at the scene.
The Occupy Oakland encampment began on Oct. 10. City Administrator Deanna Santana said the city arrested people starting at 4:30 a.m. today because conditions had deteriorated and the city could no longer maintain public health and safety and crowd control.
City officials said there were reports of sexual offenses, fighting, public drinking and intoxication and other problems at the encampment.
Oakland police said 79 arrests were made in the Frank Ogawa Plaza area near 14th Street and Broadway and six additional arrests were made at Snow Park a few blocks away near the corner of 19th and Harrison streets.
Carlos Villarreal, a spokesman for the National Lawyers Guild, which is representing many of the protesters, said he has been told that more than 100 people were arrested, mostly on misdemeanor charges.
A speaker at the rally said several people were arrested on more serious felony charges, such as resisting arrest and battery on a police officer.
Villarreal said two protesters suffered broken hands when they were arrested and one protestor was taken to a hospital with head injuries.
Law enforcement officials have closed 14th Street between Oak Street and Frank Ogawa Plaza, while protesters march.