A nighttime curfew for teenagers in the US city of Milwaukee will be strictly enforced police said Monday, following two nights of violence over the fatal police shooting of a black man.

Police in the now relatively calm Midwestern city faced off with protesters in the city's Sherman Park neighborhood on Saturday and again on Sunday after the death of 23-year-old Sylville Smith, who officials say was armed.

The death angered residents, as it echoes a series of deadly police incidents involving mainly African American suspects.

In the weekend clashes, cars and businesses were set on fire, and gunshots, rocks and bottles were aimed at police.

Fourteen people were arrested Sunday and three police cars were damaged, according to officials.

"There were groups of young people in particular, who were traveling in the streets," Mayor Tom Barrett told a news conference Monday.

"Those people, in my mind, were deliberately trying to damage a great neighborhood, in a great city."

The curfew for minors under the age of 18 begins at 10:00 pm, Barrett said.

"We're going to make sure that there is peace and order restored in this neighborhood," he told reporters.

Protests first erupted Saturday, when a crowd of about 200 turned violent following the shooting of Smith, who was in a car with another individual when he was stopped by two police officers.

Smith and the other person fled on foot. A black police officer then shot and killed Smith after he failed to drop a gun, according to authorities.

Officials said police body camera video, not yet released to the public, clearly shows that Smith had a gun and had turned around to face the officer when he was shot.

Seven police officers were injured in a second night of violence Sunday that stretched into the early hours of Monday.

On Sunday, there were 30 instances of shots fired, police chief Edward Flynn said. Officers did not return gunfire all night, in a show of "tactical and strategic restraint," he said.

Bullets struck an armored police vehicle's windshield, and a rock broke through a police car windshield, sending glass fragments into the eyes of two officers, the chief said.

Another officer's "riot helmet received a graze wound to the back of it, probably from a firearm," Flynn said, adding that the officer had not suffered serious injuries.

Some 125 members of the Wisconsin National Guard had been activated and placed on standby early Sunday, but Barrett said they were not deployed.

City politician Khalif Rainey -- who represents the Sherman Park neighborhood -- issued a plea for peace Monday, calling Milwaukee residents to "put down the bricks and put away the guns."

"Yes, our neighborhood has problems. Yes, it is unjust that many of us are denied economic opportunities because of the color of our skin and the zip code in which we were born. Yes, too many of our young people are mired in frustration, hopelessness and crime," Rainey said.

"But you can't fix the roof of a burning house."

The Milwaukee officer who shot Smith was now staying with relatives out of town for fear of his safety, Flynn said.

The officer has been placed on administrative leave, as is standard in such situations.