ST. LOUIS — In a symbolic and defiant act of civil disobedience, more than 100 protesters staged a sit-in at a QuikTrip gas station in St. Louis near the site of a police-involved shooting last week — prompting officers in riot gear to arrest nearly 20 activists.

It was the first time that any demonstrator had been taken into custody this weekend, which has been branded “Ferguson October.” Just before noon Sunday, St. Louis police said they had made 17 arrests for “unlawful assembly on the parking lot of the QuikTrip.”

St. Louis Police Chief Sam Dotson took to Twitter to accuse the demonstrators of throwing rocks at officers. “There were no reports of injuries or property damage,” said Schron Jackson, the police department’s spokeswoman. “Chief Dotson himself was nearly struck with a rock thrown at him from the crowd.”

Missourians Organizing for Reform and Empowerment, a local group that has been providing jail support for protesters, tweeted Sunday that it had been told that the arrested protesters would not be released until 2 p.m.

More than 1,000 protesters march overnight at St. Louis University to condemn the recent fatal shootings of two black teenagers by police. (Reuters)

Hundreds have swarmed greater St. Louis for demonstrations after the Aug. 9 shooting of Michael Brown, an unarmed black 18-year-old, by Darren Wilson, a white police officer.

But, unlike the marches and demonstrations earlier in the weekend, the plans for the late-night march were closely guarded. Only about several dozen of the most-active local activists in Ferguson were aware that the group would be led to the gas station and that an act of civil disobedience would take place.

Organizers even tweeted inaccurate information about when they were leaving the scene of the Shaw shooting and in what direction they were walking — in a bid to prevent preemptive police measures.

The QuikTrip was chosen in part because of the role a QT gas station in Ferguson played in the aftermath of the Brown shooting. It was burned down on the first day of protests and then became an impromptu town square and meeting place for protesters until the owners erected a fence around the lot.

In a nod to their lost meeting place in Ferguson, organizers decided to “occupy” another QuikTrip early Sunday.

First, organizers departed from protests taking place in Ferguson and began spreading the word to assemble in Shaw — at the scene of a police-involved shooting last week.

Then, with close to 100 people, they began marching down the St. Louis sidewalks around 1 a.m.

Chanting “no justice, no peace” and “the whole damn system is guilty as hell,” the marchers were on the move for close to half an hour. Blocks from the QuikTrip, officers in cruisers, trucks and large tactical vehicles began to catch up.

When the protest reached the gas station, march leaders yelled through the loud speakers: “Do not cause any destruction; this is a peaceful protest.” Then, volunteers stood guard at the gas station’s entrances to make sure no one entered or harmed the building.

Officers with large shields and other riot gear then entered the gas station lot behind the protesters, making an “L” formation around the protesters — who paused for 4½ minutes of silence for Brown.

Then, dozens locked arms and sat on the pathway in front of the entrance. Officers wielding batons and cans of pepper spray ordered them to leave and then began making arrests.

The protesters who were not arrested were pushed onto the sidewalk and then into the street, where some officers deployed pepper spray, which eventually dispersed the crowd, including many of the legal observers who were on hand. The observers initially believed the officers had used tear gas as well, but Dotson said later that only pepper spray was deployed.

Local bars were emptying out, and several area pedestrians were caught in the spray.

“I was walking home down the street and all of a sudden my eyes started burning,” said Adam Spears, 23, a resident who was not among the protesters. “I had no idea what was going on, or what I was walking into.”

When one bystander spotted Dotson, he called out and asked about whether he could continue standing on the sidewalk. Dotson acknowledged him but then turned and walked away without answering.

Just after 2 a.m. local time, Dotson — who was later seen on the scene, though it is unclear when he arrived — tweeted that protesters had thrown rocks at some officers and that arrests were being made.

A Post reporter at the QuikTrip did not observe any acts of aggression from protesters toward the police. However, he was standing on the sidewalk off of the gas station lot in compliance with police orders and could not observe the entirety of the interaction unobstructed. Protest leaders insist that no rocks were thrown at officers, many of whom were carrying video cameras.

In an interview with The Post, Dotson said the Saturday night arrests were not triggered by rocks being thrown by protesters.

Rather, it was because protesters shut down a private business and were “unlawfully” gathered on private property and refused to leave. He said pepper spray, not tear gas, was used on select individuals who pressed up against officers’ shields as they attempted to move protesters back to the sidewalk.

“There is much less chance of someone getting injured with pepper spray then if we ended up with a physical altercation between a protester and an officer,” he said. “Pepper spray was not used on the people who were passively resisting on the ground. It was directed to specific individuals who were resisting officers’ efforts to clear the grounds.”

Dotson said his officers reported to him that some rocks were thrown during the march, but no injuries were reported. The rock-throwing was not documented in photos or on video. He said that as police were clearing the crowd at the QuikTrip, a rock was thrown from the crowd toward the officers. He said it came within about 15 feet of him and was about the size of a baseball.

“I did not see the origin of the rock. I don’t know exactly where it came from,” he said.

The civil disobedience came in part due to local organizers’ frustrations with many of the Ferguson October events — which included police escorts and calm protests. Many of the local activists, who have been arrested several times since Brown’s death, have expressed anger at the often-celebratory nature of this weekend’s events.

The breaking point for some organizers was when a march to the Ferguson police station on Saturday night turned into a dance party in the streets.

“It’s disrespectful,” said Deray McKesson, one of the organizers. “This is supposed to be about showing solidarity, not a celebration.”

 An earlier version of this post said police used tear gas to disperse protesters. Police said Sunday that pepper spray was used.

Kimberly Kindy contributed to this report from Washington.

More than 1,000 protesters march overnight at St. Louis University to condemn the recent fatal shootings of two black teenagers by police. (Reuters)