FERGUSON, Mo. — Tense but peaceful protests over Michael Brown’s death and other fatal police shootings in Missouri and elsewhere stretched across the St. Louis region Friday as organizers urged hundreds of participants to avoid arrest so that they could return for a weekend of demonstrations.

The four-day event called Ferguson October began Friday afternoon with a march outside the St. Louis County prosecutor’s office in Clayton and renewed calls for prosecutor Bob McCulloch to charge Darren Wilson, a white Ferguson officer, in the Aug. 9 death of 18-year-old Brown, who was black and unarmed. A grand jury is reviewing the case.

The demonstrations moved to Ferguson Friday night as protesters stood inches from officers in riot gear before demonstrators disbursed. Many then went to the site of a police shooting in St. Louis, where another demonstration is planned Saturday. By 2 a.m. Saturday, St. Louis police had blocked a main road that crosses an interstate highway near Saint Louis University’s medical complex, but the heavy police restrictions didn’t keep hundreds more — including many newcomers from across the country who joined local residents — from marching in the streets.

“It’s important for this country to stand with this community,” said protester Ellen Davidson of New York City, a community college administrator who was making her second trip to the St. Louis area since Brown’s death. “This community is under siege. … The eyes of the world are watching.”

The planned Saturday morning protest in downtown St. Louis will take place hours before the Cardinals host the San Francisco Giants in the first game of the National League Championship Series. And on Monday, a series of planned — but unannounced — acts of civil disobedience are to take place throughout the St. Louis region.

“I’m not planning to get arrested,” said Davidson, who accompanied about 15 other members of Veterans for Peace from Illinois, Minnesota, New York and Tennessee. “But I do plan to do what I believe are in my rights as a protester. If I get arrested, that’s on the people who arrest me.”

Organizers said before the weekend that they expected 6,000 to 10,000 participants, but the initial protest outside the county courthouse, which took place amid a cold and steady rain, didn’t draw nearly that amount. Tensions increased in Ferguson, with hundreds of protesters gathering outside the Ferguson Police Department and chanting anti-police remarks such as, “Killer cops, KKK, how many kids did you kill today?” as a wall of about 100 officers in riot gear stood impassively.

In Clayton, officers escorted the several hundred demonstrators through the suburb’s downtown as they marched past high-end restaurants, jewelry stores, banks and law offices.

“We are here to demand the justice that our people have died for,” chanted protest organizer Montague Simmons of the local group Organization for Black Struggle. “We are here to bring peace, to bring restoration, to lift our banners in the name of those who’ve been sacrificed.”

Meanwhile, the St. Louis Police Department announced it had encrypted its radio communications system, saying tactical information relayed to officers had been compromised during recent events, putting officers and the public at risk.

The early Saturday morning protests took place on St. Louis’ south side, where on Wednesday night a white police officer shot and killed another black 18-year-old. Police say Vonderrit D. Myers shot at the St. Louis officer, who was in uniform but working off-duty for a private neighborhood security patrol. Myers’ parents say he was unarmed.

The officer’s name hasn’t been released. St. Louis police arrested eight people Thursday as hundreds gathered to protest Myers’ death. At one point officers used pepper spray to force protesters back. A police spokeswoman said one officer was struck in the arm after someone threw a brick, and several cars were damaged.

Black leaders in St. Louis want the Justice Department to investigate Myers’ shooting as well. Police said the officer fired 17 rounds after Myers shot at him. Preliminary autopsy results show a shot to the head killed Myers. The officer wasn’t injured.