SAN FRANCISCO, California (AFP) - Americans angry at the acquittal of Mr George Zimmerman in the death of black teen Trayvon Martin marched in US cities throughout Saturday night, with reports of sporadic acts of violence.
Spontaneous marches of varying sizes erupted in cities including San Francisco, Chicago, Washington, Atlanta and Philadelphia.
A jury in Sanford, Florida late on Saturday found Mr Zimmerman, a volunteer neighbourhood watchman, not guilty of shooting dead Martin, a 17 year-old unarmed teen on the night of February 26, 2012.
The trial has riveted the nation for weeks, and emotions came to a boiling point as news of the verdict spread.
Prominent rights activists like Jesse Jackson appealed for calm.
"Avoid violence, it will lead to more tragedies. Find a way for self construction not deconstruction in this time of despair," he wrote on Twitter.
Martin's parents have long called for non-violent demonstrations, quoting civil rights icon Martin Luther King and the Bible.
Several hundred demonstrators marched peacefully amid a heavy police presence in downtown San Francisco soon after the verdict.
Many carried signs with slogans such as "The people say guilty". Hours later, angry protesters marching through Oakland - just across the bay from San Francisco - spray-painted cars and smashed windows, helicopter video footage posted by the Oakland Tribune showed. One vandalised vehicle was a police cruiser.
In Chicago, to the cry of "No justice, no peace! No racist police!" a crowd of activists held a noisy downtown rally, the Chicago Tribune reported, while protesters gathered at Times Square in New York City to vent their anger.
Los Angeles police declared a "citywide tactical alert" when some 200 demonstrators gathered at a park in a historical black neighborhood to demonstrate, but police later told local media that it was as a precaution, and that there had been no acts of violence.
In Washington, dozens of mostly African-American youths marched chanting slogans in a city neighbourhood. They were followed closely by patrol vehicles, an AFP journalist reported.
A crowd of several hundred gathered all day on Saturday outside the courthouse in Sanford, Florida - and many were outraged when the verdict was read.
"It's the end of our justice system," said Mr Ashton Summer, a 20 year-old Puerto Rican. "Justice is not equal for everyone."
The ANSWER coalition, which helped organise large protest rallies during the Iraq war, said it would hold marches on Sunday in seven US cities, as well as three separate ones in New York.
"We are very saddened by the jury's verdict," said Martin family attorney Benjamin Crump after the verdict was read. "The family is heartbroken."
Rights activist Al Sharpton posted a statement on Facebook describing Mr Zimmerman's acquittal as "a slap in the face to the American people". "We intend to ask the Department of Justice to move forward as they did in the Rodney King case and we will closely monitor the civil case against Mr Zimmerman," he said.
Rodney King was an African-American man who was beaten by Los Angeles police following a car chase in April 1991. The beating was videotaped and aired on television, sparking widespread outrage.
Days of violent rioting and looting broke out in Los Angeles when the police officers involved in the beating were acquitted in April 1992.
Mr Benjamin Todd Jealous, head of the NAACP, the premier US civil rights group, said his organisation is "outraged and heartbroken" over the verdict.
"We will pursue civil rights charges with the Department of Justice, we will continue to fight for the removal of Stand Your Ground laws in every state, and we will not rest until racial profiling in all its forms is outlawed." The controversial laws allow people who fear for their lives to use deadly force to defend themselves without having to flee a confrontation.
"The jury found he acted appropriately in defending his life in accordance with the law," George's brother Robert Zimmerman Jr said on CNN.
"I think that conjecture and speculation and emotional reaction to what people think may or may not have happened has been dominating the discussion for a long time."