OAKLAND -- As President Barack Obama began pressing the flesh Monday in Oakland, hundreds of medical cannabis supporters took to the streets, marching past equally thick crowds of Obama supporters who stood in line for hours to see the president during an evening fundraiser at the Fox Theater.

While most of the cannabis protesters have dispersed, by 6:30 p.m. more than 100 demonstrators with Occupy Oakland and various anti-war groups had amassed at the corner of 19th Street and Broadway, blocking traffic along the thoroughfare.

The protesters, several of whom had bandannas covering their faces, were remaining behind police barricades, one block from the theater.

Audio: Cannabis protest leading up to Obama's visit

Obama, making his first visit as president to Oakland, touched down shortly before 3 p.m. with Mayor Jean Quan and Congresswoman Barbara Lee there to greet him.

People cheered his motorcade as it passed by the Oakland Public Library on its way to a campaign event at the Scottish Rite Center near Lake Merritt, where the president met with business and city leaders, including Police Chief Howard Jordan and City Administrator Deanna Santana. About two hours later spectators on Madison Street waived and applauded as the motorcade ferried Obama to a fundraiser in Piedmont.

The scene was different downtown where demonstrators amassed to protest Obama's positions on illegal immigration, gay marriage, the war in Afghanistan and drug enforcement.

At 3 p.m. more than 300 medical cannabis supporters began marching up Broadway, stopping traffic as they looped around the downtown. Protest leaders in green vests called attention to anyone they saw with their faces covered in an attempt to keep the peace. Most in the crowd marveled at the shear numbers they were able to marshal.

"We dreamed of a movement like this 20 years ago," said Caroline Hamilton, 49, of Oakland. "It seemed so unattainable. But we're still so far from the goal."

Police said they arrested three people by the time the president finished his speech at the Fox, about 8:30 p.m. Authorities withheld the identity of the people arrested until they could confirm the names and other personal information.

Officers arrested the first man at 3 p.m. in the 600 block of William Street. Oakland Police Sgt. Chris Bolton said police arrested the man on a $10,000 warrant for violating an order to stay away from Frank Ogawa Plaza issued during past Occupy Oakland activities. At 3:30 p.m. a second man was detained, this time in the 1900 block of Broadway, according to Bolton. The protester walked up to an officer sitting in a marked patrol cruiser, pointed a bull horn at the officer's ear and sounded the air blast horn, he said.

About 7:15 p.m. police said they took a woman into custody following a citizen's arrest in the 1700 block of Telegraph for battering an 11-year-old child.

The Fox at 1807 Telegraph Ave. is in the heart of Oaksterdam, a district dotted with cannabis-related businesses and home base for several of the industry's leaders. Many storefronts along Broadway hung green banners to show solidarity with the medical cannabis cause.

Medical cannabis advocates are angry with the president for allowing federal prosecutors to shut down dispensaries across California after he had pledged during his first campaign not to target the industry in states where it is legal.

Hundreds of dispensaries have been closed since October. In April, agents raided the Oakland properties of former Oaksterdam University Chief Richard Lee, who bankrolled a failed 2010 state proposition to legalize cannabis. Two weeks ago, prosecutors moved to shut down Oakland's Harborside Health Center, the nation's largest dispensary.

Harborside's Steve DeAngelo again pledged to stay open, but said cannabis protesters wouldn't stick around this evening to take their message directly to Obama. "We're not here to confront the president or embarrass him or get in the way of this event," he said.

While Cannabis supporters marched and chanted, hundreds of Obama supporters were already lined up at Broadway and 19th Street waiting to get into the 4:30 p.m. fundraiser at which Obama is scheduled to speak at 7:55 p.m. Unlike an afternoon event in Piedmont where the entrance fee was $35,800, the event at the Fox had tickets for as little as $100.

"It means a lot that the president has come to Oakland where I live and not up in hills where the millionaires are," said Mada Hudson, who was wearing an Obama shirt. "I don't have $35,000 to see him, but I've got $100."

Christian Weber of Redwood City began waiting in line on Broadway with his wife and 11-year-old son shortly before 2 p.m. "It has a little bit of a rock concert atmosphere," he said. "It's a historic occasion. I think my son will look back and say, 'Hey, I saw President Obama.'"

Oakland, which has been plagued by periodically violent Occupy Oakland protests since October, is implementing numerous security restrictions for Obama's visit. Police began barricading streets adjacent to the Fox early Monday morning making it impossible to get within a block of the theater.

Telegraph and San Pablo avenues are closed from 16th Street to Thomas L. Berkley Way (20th Street). Several side streets also are closed from Broadway to San Pablo. The street closures are scheduled to remain in effect until 10 p.m. Broadway remains open.

AC Transit is altering 12 routes between 11 a.m. and 11 p.m. and warning passengers to expect delays through downtown Oakland. BART has closed the 17th Avenue entrance to the 19th Street BART Station.

The protests began at noon with about 200 medical cannabis supporters rallying outside City Hall, a few blocks from the theater. Several patients urged the president to direct authorities to focus on illegal guns and foreign drug cartels.

"It's time that our country gets its priorities straight," said Steve Raucher, a 61-year-old from Walnut Creek said.

Steph Sherer, executive director of Americans for Safe Access, said Oakland's protests were an inspiration to medical cannabis activists nationwide. "They know if Oakland can turn out 600 people, then they can do it in their communities as well."

Staff Writers Matt O'Brien, Angela Woodall and Anna Gallegos contributed to this story

Contact Matthew Artz at 510-208-6345.

AC Transit Impacts
AC Transit has implemented the following detours from 11 a.m. until 11 p.m.:
Lines 1 and 1R to Berkeley will serve regular stops on 12th Street at Broadway and on Telegraph Avenue at 24th Street, but not regular stops between those points.
Lines 1 and 1R to Bay Fair BART will serve regular stops on 11th Street at Broadway and on Telegraph Avenue at West Grand Avenue (Line 1) or Telegraph Avenue at 24th Street (lines 1 and 1R), but not regular stops between those points.
Line 11 to the Dimond District will serve regular stops on Harrison Street at 21st Street and on 7th Street at Jackson Street, but not regular stops between those points.
Line 11 to Piedmont will serve regular stops on 8th Street at Jackson Street and on Harrison Street at Grand Avenue, but not regular stops between those points.
Line 12 to downtown Berkeley will serve regular stops on 11th Street at Clay Street and on Grand Avenue at Webster Street, but not regular stops between those points.
Line 12 to downtown Oakland will serve regular stops on Grand Avenue at Valdez Street and its terminal on 10th Street at Washington Street, but not regular stops between those points.
Line 18 to Montclair will serve regular stops on Martin Luther King, Jr. Way at 25th Street and on 11th Street at Franklin Street, but not regular stops between those points.
Line 18 to Albany will serve regular stops on 12th Street at Broadway and on Martin Luther King, Jr. Way at 22nd Street, but not regular stops between those points.
Line 51A to Fruitvale BART will serve regular stops on Broadway at 25th Street and on Broadway at 9th Street, but not regular stops between those points.
Line 51A to Rockridge BART will serve regular stops on 8th Street at Broadway and on Broadway at Grand Avenue, but not regular stops between those points.
Line 58L in both directions will serve regular stops on Grand Avenue at Perkins Street and on Broadway at 7th Street, but not regular stops between those points.
Lines 72 and 72M to Oakland Amtrak will serve regular stops on San Pablo Avenue at West Street and on Broadway at 9th Street, but not regular stops between those points.
Line 72R to Oakland Amtrak will serve regular stops on San Pablo Avenue at Market Street and on Broadway at 7th Street, but not regular stops between those points.
Lines 72, 72M, and 72R northbound will serve regular stops on Broadway at 9th Street (lines 72 and 72M); Broadway at 7th Street (lines 72, 72M, and 72R); and on San Pablo Avenue at West Grand Avenue, but not regular stops between those points.
Line NL in both directions will serve regular stops on Grand Avenue at Perkins Street and on West Grand Avenue at Market Street, but not regular stops between those points.
The Broadway Shuttle to Jack London Square will serve regular stops on Grand Avenue at Webster Street and on Broadway at 11th Street, but not regular stops between those points.
The Broadway Shuttle to Grand Avenue will serve regular stops on Broadway at 11th Street and its terminal on Grand Avenue at Webster Street, but not regular stops between those points.
To facilitate transfers, lines 1 and 1R to downtown Berkeley; 12 to downtown Berkeley; 18; 51A to Rockridge BART; 72, 72M, and 72R northbound; and the Broadway Shuttle to Grand Avenue will serve temporary stops on Castro Street between 12th and 17th streets.

Oakland Street Closures
Oakland is planning to close the following streets from 8 a.m. to 11 p.m. Monday:
Telegraph Avenue between 16th Street and Thomas L. Berkley Way (20th Street)
San Pablo Avenue between 16th Street and Thomas L. Berkley Way
Rashida Muhammad Street between 19th and 20th streets
William Street between Telegraph and San Pablo avenues
16th Street between Broadway and San Pablo
17th Street between Broadway and San Pablo
18th Street between Telegraph and San Pablo
19th Street between Broadway and San Pablo