Police in the US city of St. Louis shot dead another suspect, a short distance from a suburb that is the scene of protests over the killing of an unarmed black teenager.
St. Louis Police Chief Sam Dotson said in a tweet that officers had responded to a call and found an apparently agitated man, armed with a knife who yelled "kill me now" and approached the patrol.
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In a tweet from his own account retweeted by his force, Dotson said: "Officers gave suspect verbal commands. Officers feared for their safety and both officers fired their weapons. Suspect is deceased."
Dotson said the suspect, a 23-year-old African-American male, had been involved in a convenience store theft and was seen acting eratically.
Both officers fired at the suspect, killing him.
"Every police officer out here has the right to defend themselves," Dotson told reporters.
Ferguson Mayor James Knowles said that he is concerned the fatal shooting will give "agitators" another reason to riot.
"The slightest thing can inflame people's anger," the mayor said on CNN.
Earlier on MSNBC, Knowles said racial tensions are not present in Ferguson.
“I don’t believe that’s the case," Knowles said. "There’s not a racial divide in the city of Ferguson."
“According to whom?” MSNBC's Tamron Hall replied. “Is that your perspective, or do you believe that is the perspective of African-Americans in your community?”
“That is the perspective of all residents in our city, absolutely,” Knowles said.
Photos tweeted by reporters in the area of Tuesday's fatal police shooting show tense moments followed by relative calm.
The world's media descended on the street where the latest police shooting took place, dozens of reporters having been in the nearby St. Louis suburb of Ferguson covering the ongoing unrest.
Onlookers gathered at the yellow incident tape sealing off the scene of the shooting outside a convenience store in St. Louis, some of them chanting the slogan of the protests: "Hands up, don't shoot."
Captain Ed Kuntz told reporters at the scene that an investigation had been launched, but, based on what he had heard, "it seems reasonable to say it was justifiable."
"Whenever there's a police shooting, tensions are always more high," he admitted, while insisting: "Right now we are focused on preserving life and protecting property."
On August 9, 18-year-old Michael Brown was killed in broad daylight on a residential street by Darren Wilson, a 28-year-old white police officer -- triggering a wave of community protests.
Although police have since fingered Brown as a robbery suspect, he was unarmed at the time of shooting and some witnesses have said he was surrendering when he was hit six times, twice in head.
In the past ten days, this mainly black suburb of St Louis, Missouri has become a global symbol of the tensions created by the United States' racial divide and heavy-handed law enforcement tactics.
Overnight, protesters shot at police and threw rocks and firebombs in a new spasm of violence that left six wounded and led to 31 arrests.
Police responded with tear gas to disperse the crowd of about 200 in the town, Captain Ron Johnson of the Missouri Highway Patrol said.
Johnson said two demonstrators and four officers were injured, and argued that police had showed restraint by not opening fire.
The demonstrations started peacefully, only hours after President Barack Obama, made a televised appeal for calm.
But, according to Johnson, a loud group of about 200 moved toward the police and a small minority among them attacked officers in riot gear.
"There is a dangerous dynamic in the night," Johnson said.
"It allows a small number of violent agitators to hide in the crowd and then attempt to create chaos."
He added: "Our officers came under heavy gunfire."
Johnson stood behind a table on which a gun and a Molotov cocktail he said had been seized from protesters were on display.