NEW YORK - Tens of thousands of protesters across the United States took to the streets on Saturday to protest against two separate grand juries' decisions not to indict white officers involved in killing unarmed African-Americans during arrests.

In a massive protest in New York City on Saturday, thousands of protesters chanted slogans such as "What do we want? Justice! When do we want it? Now!" "No justice, no peace." as they matched from Washington Square Park to the New York Police Department headquarters.

The New York event, named as "Millions March NYC", was the latest of a series of protests in a response to recent decisions by two separate grand juries in Ferguson, US State of Missouri, and Staten Island, New York City, which declined to indict the white police officers responsible for the deaths of 18-year-old Michael Brown and 43-year-old Eric Garner.

Organizers of "Millions March NYC" said in a statement that they hoped millions of people would go peacefully into the streets all over the country to express their anger and demand justice for victims of police violence and institutionalized racism.

"We are continuing where the freedom fighters of the Civil Rights Movement left off. We are a new generation of young multi-racial activists willing to take up the torch and we're not going to stand for this anymore," said the statement.

Among other demands, the "Millions March NYC" said it also wanted the establishment of an independent prosecutor office to handle cases of police misconduct and excessive use of force.

That same message was echoed by protesters in "Justice For All" march in US capital Washington, where nearly 10,000 protesters marched through the city to call for justice and decry racial discrimination.

The "Justice for All" march, organized by the National Action Network, a civil rights organization, was joined by families of police shooting victims, including relatives of Garner, Brown and other victims in racial profiling such as Tamir Rice and Akai Gurley.

Other cities, including Chicago, Los Angeles and San Francisco, also held similar protests on Saturday.

In recent weeks, protesters around the country have participated in demonstrations to decry racial injustice and police brutality. Many of their signs and chants contain the slogan that has become synonymous with the movement: "Black Lives Matter".

One African-American man from Chicago, Michael, told Xinhua that black people "are consistently being attacked" and they "are victims of mass incarceration."

"We want the police to be our police in each district. We don't want to be profiled anymore. We want the system to change, and we want the power and ability. As voters, we have the right to do that," Michael said.

Garner, a father of six, died in July after police officers attempted to arrest him for allegedly selling untaxed cigarettes in one of New York's boroughs Staten Island.

In another case, Michael Brown, 18, was fatally shot by Officer Darren Wilson in Ferguson, Missouri in August.

The decisions by grand juries in two different states not to charge the white officers involved in both cases have so far triggered weeks of protests across the country.