Thousands of people rallied in the streets of downtown Los Angeles Friday afternoon for annual May Day marches supporting rights for workers and immigrants, with an emphasis on pushing for a $15 minimum wage and implementation of President Barack Obama's executive orders on immigration.

Map: May Day Street Closures

The Los Angeles Police Department declared a citywide tactical alert ahead of the planned marches, alerting personnel that they may be deployed to meet staffing requirements in response to large-scale events like Friday's rallies and marches. The events are expected to make life difficult for afternoon commuters in downtown Los Angeles, with street closures planned throughout the area to accommodate what are expected to be massive crowds.

In an annual theme, police are urging motorists to avoid the area if at all possible and plan alternate routes. A pair of marches are planned downtown, with participants expected to begin rallying at 3 p.m. and marching at 4 p.m.:

International Workers March: Participants will gather at Olympic Boulevard and Broadway, then march north on Broadway to Grand Park at Broadway and First Street.

Full Rights March: Participants will gather at Cesar Chavez Avenue and Broadway, march east on Cesar Chavez, south on Main Street, east on Aliso Street, south on Alameda Street then west on Temple Street, again ending at Grand Park.

The theme of the Full Rights March is "On May Day, No Justice Delayed," pushing for an increased minimum wage, implementation of Obama's orders to protect millions of immigrants from deportation and an end to police violence.

The Los Angeles City Council is debating a proposal to raise the minimum wage from $9 an hour to $13.25 an hour by 2017, to $15.25 an hour by 2019, and higher levels in subsequent years based on the Consumer Price Index. Supporters of the wage hike proposal say it will lift hundreds of thousands of low-wage workers out of poverty and that businesses are capable of absorbing the increased costs, while critics of the plan say it would drive businesses out of the city and slow job growth.

Los Angeles County officials are also conducting studies on a possible hike in the minimum wage.

On the immigration front, millions of immigrants are awaiting the outcome of federal litigation over Obama's "deferred action" orders, which have been put on hold by a judge in Texas. Opponents of the orders -- most notably Republicans in Congress -- contend Obama overstepped his authority in issuing them.

The annual downtown Los Angeles rallies have been mostly peaceful, but marches in 2007 ended in violence when police and demonstrators clashed in MacArthur Park, located northwest of downtown Los Angeles in the Westlake neighborhood. The confrontation resulted in lawsuits and an examination of LAPD crowd control policies.

For more than a century, International Workers' Day has been celebrated on May 1 to mark the 1886 Haymarket Riot in Chicago, when a bomb turned a worker rally into a deadly event. The marches have roots in labor movements calling for worker rights.

But it recent years, demonstrations in the United States have taken up various timely causes.

Activists in cities from Boston to Oakland, California, said they are also rallying in support of "Black Lives Matter" -- the slogan of the growing movement in the wake of a series of high-profile deaths of black men as the result of a police encounter. The move comes after unrest in Baltimore and protests in other cities over the death of Freddie Gray, who suffered severe spinal injuries at some point after he tried to run from police April 12.