CLEVELAND — Protests turned violent on the third day of the Republican National Convention here, as more than a dozen people were arrested. 

The Cleveland Police Department said 18 people were arrested, two for felonies, after a protester burned an American flag.

Flag was set on fire. Cops used pepper spray to break it up. Melee erupted #RNCinCLE pic.twitter.com/K6MGSjKI7L

— James Queally (@JamesQueallyLAT) July 20, 2016

Police Chief Calvin Williams said police moved in after the protester lit himself on fire. He emphasized that burning a flag is in itself legal.

The two felony arrests were for assaulting a police officer — Williams said the assault occurred as authorities moved to extinguish the fire.

Williams said an officer was punched, and a dispersal order was then given. Others who did not disperse were arrested, he said.

In a Twitter post, the Cleveland Police Department said there were no serious injuries.

The protest outside the convention arena was the most physical confrontation with police yet here. 

Moment that scuffle erupted outside Q entrance leading to multiple arrests, two officers injured #RNCinCLE #RNC2016 pic.twitter.com/6l8cUhCSer

— Jesse Byrnes (@jessebyrnes) July 20, 2016

Police attempted to create a line between several protesters with their arms locked in a circle before the scene quickly escalated. At least one officer used a fire extinguisher on a group of protesters, while Cleveland police rolled in on bicycles and created a makeshift barricade around the detained protesters.

Mounted officers were on scene, along with about two dozen troopers in riot gear. 

Earlier in the day, a group blocked off a large portion of the main entrance to the Republican National Convention.

The protesters, a group that swelled to approximately 100 people, held tan sheets portraying a border wall and called to “wall off Trump.”

Other protest groups joined that march, holding portions of the fake wall to extend it several hundred yards in front of the main Quicken Loans Arena entrance.

Cleveland cops with bikes holding perimeter, with state patrol in secondary row and cops on horses/riot gear inside. pic.twitter.com/InHALfCoIJ

— Jesse Byrnes (@jessebyrnes) July 20, 2016

Police holding a very loose line around taped off materials on the ground where protesters were standing.#RNC2016 pic.twitter.com/JZpHYhgOeZ

— Jesse Byrnes (@jessebyrnes) July 20, 2016

Updated 9:40 p.m.