Black Lives Matter protesters chant slogans at the Mall of America light rail station in Bloomington, Minnesota December 23, 2015. [Photo/Agencies]

BLOOMINGTON - Black Lives Matter held demonstrations in Minnesota and California on Wednesday to protest police killings of unarmed blacks, dubbing the day "Black Xmas" to show it could affect the economy on one of the busiest shopping days of the year.

"Black communities across the United States are taking brave actions to impede the flow of goods and commerce with peaceful protests to call for an immediate overhaul of the justice system," Black Lives Matter said in a statement on Facebook.

"There will be no business as usual until we get accountability for our dead, and justice for the living," the group said. "Instead of buying gifts to fuel this system, Black Xmas is a day of action."

The loosely organized movement grew out of protests over police killings of black men in Ferguson, Missouri, New York and other cities.

Citing the lack of an indictment Monday related to the death of Sandra Bland, a black woman who died by hanging in an apparent suicide in a jail cell following a controversial traffic stop, Black Lives Matter on Wednesday called for police accountability and the removal of grand juries in cases involving police shootings.

In Minnesota, four demonstrators were arrested at the Mall of America in Bloomington, a Minneapolis suburb, where a planned protest over the police killing of an unarmed black man by Minneapolis police last month was swiftly broken up.

Black Lives Matter demonstrators camped outside a Minneapolis police station for nearly three weeks after a police officer shot Jamar Clark, 24, on Nov. 15.

The death of Clark, who was unarmed, added fuel to an already heated debate over race and justice following several such killings across the United States in the past year.

"It's been sleepless nights," Jamar's cousin, Alexander Clark, said at the mall demonstration just before police took him into custody, adding: "We are here for justice for my cousin." It was not immediately clear whether Clark had been formally arrested.