LOS ANGELES, Nov. 25 (Xinhua) -- Protests over the grand jury decision not to prosecute a white police officer for the fatal shooting of a black teenager in Ferguson, Missouri, continued Tuesday in Los Angeles.

Around 150 protesters marched through South Los Angeles to downtown in the afternoon. Some of them ran into a skirmish line of police and some marchers jumped on top of police cruisers.

Protesters carried signs with slogans such as "Not Anti-Cop; Anti-Brutality" and "Arrest Darren Wilson", the Ferguson police officer who shot dead Michael Brown on Aug. 9.

On Tuesday morning, the Los Angeles Police Department declared another citywide tactical alert in anticipation of more protests.

The alert allows the department to keep officers on duty beyond their normal shifts, as more protests are planned in the area in response to the grand jury decision in Ferguson.

Los Angeles police Chief Charlie Beck told the media that while lawful protests will be respected, people who break the law or try to stop freeway traffic will be arrested.

"Last night, in response to the decision in Ferguson, a number of folks in Los Angeles participated in lawful protest," Beck was quoted by local media as saying, "that lawful protest was facilitated for many hours by the Los Angeles Police Department."

"We want to make sure that everybody knows that we absolutely support the First Amendment," he added.

"We support people's right to assemble and to lawfully speak out on issues that are of great concern to them. ... However, we cannot support -- and we will not allow -- people to use their rights to trample on the rights of others, and that includes such things as vandalism, violence, and in particular an incident that we had last night (of) going up on one of our freeways," said Beck.

Three people were arrested overnight during protests that erupted around Los Angeles in response to the Ferguson ruling. One person was arrested on suspicion of assault on a police officer, one for failure to disperse and one for public intoxication.

Police officers fired some "less lethal" foam rounds to keep people from going onto freeways, said Beck.

A grand jury finding that Officer Darren Wilson will not be indicted for the shooting of unarmed Michael Brown triggered protests in many cities across the United States.

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