FERGUSON, Mo. — Activists on Saturday called for mass civil disobedience on the highways in and around this St. Louis suburb to protest the killing of an unarmed black teenager by a white police officer, with the leaders of one coalition encouraging supporters to stop their cars to tie up traffic on Labor Day.

The appeal came at a peaceful if at times tense march and rally on Saturday that drew what appeared to be well more than 1,000 demonstrators to some of the same Ferguson streets where the police clashed with protesters in the days after the killing of Michael Brown. Mr. Brown, 18, was shot Aug. 9 by Officer Darren Wilson of the Ferguson Police Department, and his bloody body lay on Canfield Drive for about four and a half hours before it was removed.

Organizers at the rally called on demonstrators to drive on Interstate 70 and other area highways at 4:30 p.m. Monday, turn their hazard lights on and stop their vehicles for four and a half minutes to symbolize the four and a half hours that Mr. Brown’s body lay in the street.

“We’re going to tie it down, lock it down,” Anthony Shahid, one of the lead organizers of the rally, told supporters from the stage at a park. The following week, if the coalition’s demands were not met, including that Officer Wilson be fired and arrested on charges of murder, another four-minute traffic shutdown would occur on two days instead of just one, he said.