Police shot tear gas and smoke canisters at protesters in Ferguson, Missouri, overnight, with authorities blaming outsiders for bringing a criminal element to the St. Louis suburb following the police shooting death of unarmed teen Michael Brown.
Incidents from a "tiny minority of lawbreakers" prompted the police response, including shots fired and Molotov cocktails thrown, Missouri State Highway Patrol Capt. Ron Johnson said, speaking at an early-morning news conference.
"Our officers came under heavy gunfire," he added.
Two people were shot and at least 31 people were arrested during Monday night's unrest, Johnson said, with some of those arrested coming from as far away as New York and California.
Four St. Louis police officers were hit by rocks and bottles and sustained injures, Johnson said.
Read More: Brown Could Have Survived First 5 Shots, Last Shot Killed Him: Autopsy
Read More: 'State of Emergency' in Ferguson, Missouri
Protesters stood defiantly in the middle of the street amid the smoke and confusion. The tear gas hit journalists on the scene, too.
Police marched on the protesters and, shortly after, told members of the media that shots had been fired and that they should move to the command center.
Johnson said journalists need to be more mindful of police efforts.
"In the midst of chaos, trying to move people along, we have to be safe," Johnson said.
Johnson encouraged protesters to rally during the daytime hours.
Just before the clashes picked up, Missouri Gov. Jay Nixon shared encouraging messages online, tweeting, "Let's show the world that we can protest peacefully & passionately. Let's keep #Ferguson safe tonight." He also tweeted a photo of himself speaking earlier in the day with President Obama.
Obama denounced the ongoing clashes at a Monday press conference. Attorney General Eric Holder will travel to Ferguson Wednesday to meet with FBI and Department of Justice officials working the case, Obama said.
National Guard troops, called in by Gov. Jay Nixon Monday, protected the police command center.
Brown, 18, was shot to death Aug. 9 by a Ferguson police officer.
'Tiny Minority of Lawbreakers' Blamed for Ferguson Unrest