Protests racked this St. Louis suburb for a fifth straight night Wednesday as anger flared anew over the police killing of an unarmed young black man.

Armored personnel carriers and officers wearing body armor and carrying assault rifles greeted demonstrators. When the crowd ignored orders to disperse, officers unleashed tear gas and rubber bullets, witnesses said.

Police sealed off the area that was the scene of vandalism and looting Sunday night.

“We’ve done everything we can to demonstrate a remarkable amount of restraint,” St. Louis County Police Chief Jon Belmar said in an interview outside the command post. “If there was an easy way to fix this, we would have already solved the problem.”

Officers had heard sporadic gunfire, he said. At least 10 people were arrested.

One of them was St. Louis Alderman Antonio French, a friend of his, Liz Peinado, said in a Twitter post. During the unrest, French has posted videos on social media of protests and the police presence on the streets. His arrest could not be independently confirmed late Wednesday.

Gov. Jay Nixon tweeted that he was canceling planned appearances to visit the area Thursday. He added: "Closely monitoring situation....  Ask for calm & urge law enforcement to respect rights of residents & press."

President Obama was briefed on the situation, a White House spokesman tweeted.

During the nighttime confrontation, protesters with shirts wrapped around their faces held signs that read, “Hands up, don’t shoot,” as police closed in on the crowd. The slogan has been adopted by protesters because witnesses said 18-year-old Michael Brown was running with his hands in the air when a policeman shot him to death Saturday in Ferguson.

In live amateur video posted to social media, police could be overheard telling the group to get out of the area or they would be arrested. Clouds of tear gas were visible in the background.

The latest unrest came hours after St. Louis County Prosecutor Robert McCulloch said details about the Brown shooting would not be released any time soon.

“We are still in the information-gathering part of the investigation,” McCulloch said in a televised news conference.

He urged anyone with information to come forward and promised that every piece of evidence would be reviewed, presented to a grand jury and eventually made public.

By withholding details from the public during the criminal inquiry, investigators would be better able to gauge witnesses’ credibility, he said.

Along with the St. Louis County Police Department, the FBI and civil rights attorneys from the Justice Department are conducting parallel investigations.

Racial tension has simmered since Saturday’s shooting, beginning with a protest late that day. Then, on Sunday night, vandals rampaged through 12 businesses, burning one and breaking windows.

Ferguson is a working-class suburb of 21,000, where two-thirds of residents are black but police and city officials are predominantly white.

Although the largest protests have been peaceful, demonstrations have turned ugly at night.

Mostly, the protests have been bloodless. But about 1 a.m. Wednesday, St. Louis County police said, an officer shot and critically wounded a man who had pointed a handgun at the officer near the site of the Brown shooting.

Earlier Wednesday, Ferguson Police Chief Thomas Jackson said he would not identify the officer involved in the Brown shooting because a rumor had misidentified the officer and prompted death threats.

The officer who shot Brown was injured in the confrontation and the “side of his face was swollen,” Jackson said. The officer was treated at a hospital, the chief said, and he was “very shaken.”

Jackson said the department has asked protesters to rally only during daylight hours to ensure community safety.

Local law enforcement authorities released only a few details about the shooting, and several witnesses have disputed the police account.

Brown had been walking down a street with a friend Saturday about noon when, according to police, an officer drove up and attempted to get out of his patrol car, and Brown pushed the officer back into the car.

After an altercation over a weapon in the car, the officer and Brown got out of the vehicle, and the fatal shooting occurred, according to Belmar, the St. Louis County police chief. Bystanders said Brown had raised his hands to surrender when the fatal shots occurred.

Wednesday evening, a brief contretemps occurred when two journalists were taken into custody.

The reporters — one from the Washington Post, the other from the Huffington Post — were quickly released after the intervention of Jackson, Ferguson’s police chief.

Twitter: @mattdpearce

Times staff writers Ryan Parker and Lauren Raab in Los Angeles contributed to this report.