NEW YORK CITY: Thousands protested in cities across the US Sunday against the acquittal of neighborhood watchman George Zimmerman, a day after his trial for killing unarmed black teenager Trayvon Martin ended in Florida.

Demonstrators rallied noisily, but peacefully, in US cities including New York, San Francisco, Boston and Chicago.

In Los Angeles, police in riot gear deployed along Hollywood Boulevard, but they were not needed as the rally proceeded without incident. But about 150 protesters blocked traffic on a freeway elsewhere in the city, local media reported.

In the pre-dawn hours demonstrators smashed windows and vandalized cars in Oakland, California.

Spontaneous marches were also held in Washington, Philadelphia, Atlanta and the Florida state capital Tallahassee. The most numerous rally Sunday was in New York City, where several thousand -- including families with children -- marched to Times Square under the watchful eye of police.

Many in the multi-racial crowd brandished signs bearing a portrait of Martin, while some, despite sweltering July heat, wore “hoodie” sweatshirts, as the 17-year-old did the night he was killed in February 2012.

“I am appalled,” said Carli VanVoorhis, a 21-year-old hairdresser.

“The man was armed, the kid was not, and the man with the gun got away,” she said. “If we say it was not a racial issue, we would be lying.”

The case has, since the beginning, pitted those who belive that Zimmerman, a 29-year-old Hispanic neighborhood watchman, killed Martin in self-defense, and those who believe it was a murder sparked by racist assumptions.

According to Florida's controversial “Stand Your Ground” law, people who fear for their lives can use deadly force to defend themselves without having to flee a confrontation. Other states, including Texas, have similar rules.

The killing also resonated among those calling for stricter gun laws like New York Mayor Michael Bloomberg, who slammed what he called “shoot-first laws.”Sadly, all the facts in this tragic case will probably never be known. But one fact has long been crystal clear: 'shoot first' laws like those in Florida can inspire dangerous vigilantism and protect those who act recklessly with guns,” Bloomberg said in a statement.

He reiterated his call to eliminate such laws.

“The tragic death of Trayvon Martin, an unarmed child attempting to walk home from the store, will continue to drive our efforts.”