Protesters marched through cities across the United States on Friday night chanting "I can't breathe" and "Hands up, don't shoot" on the eve of a large protest planned for Washington, D.C., on Saturday.
Hundreds of demonstrators took to the streets to protest recent police killings of African Americans.
More than 500 marchers in Cambridge, Mass., staged a "die-in" at Central Square near Harvard University while church members in Washington, D.C., held a long candlelight vigil along 16th Street in remembrance of those killed by police.
Earlier in the day, church leaders from New York City led a demonstration and prayer vigil on the steps of City Hall.
The protests are building up to Saturday's "justice for all" march being organized in Washington, D.C., by various groups including the Rev. Al Sharpton's civil rights organization, National Action Network.
"This issue isn't going away. In fact, the calls for justice are getting louder," Sharpton said on his television show Friday.
Sharpton said he would be joined at the march by the families of Eric Garner, Michael Brown, Tamir Rice and Trayvon Martin.
Brown, 18, was shot to death Aug. 9 in Ferguson, Mo., and Garner, 44, died July 17 after police used an apparent chokehold to subdue him on Staten Island, N.Y.
Rice, a 12-year-old Cleveland boy, was shot and killed by a white police officer who mistook his toy gun for a weapon.
Trayvon Martin was the unarmed black teenager killed by nieghborhood watch George Zimmerman in Florida. Zimmerman, a neighborhood watch volunteer, was later acquitted on all charges.
"Everyone should stand up," Sharpton said. "The only way that wrong can persist, to paraphrase Dr. King, is when good men and women sit and do nothing."
Organizing groups, including the National Assn. for the Advancement of Colored People and the National Urban League, are urging Congress to take legislative action to combat racial profiling and police discrimination, the NAACP said in a statement.
"This march is one of many demonstrations to show Congress, the country and the world that we will not stand down until systemic change, accountability and justice in cases of police misconduct are served for Michael Brown, Eric Garner and the countless other men and women who lost their lives to police abuses of authority," said NAACP President & Chief Executive Cornell William Brooks in a statement.