US riot police have hurled tear gas and marched on rioters in the St Louis suburb of Ferguson, wracked by race riots since police shot dead an unarmed black teenager.
Police tried to disperse the mob of mostly young people about three hours before the midnight curfew came into effect.
Some of the youths carried signs protesting police brutality, many had their hands up in surrender and others threw the tear gas canisters back at police.
Guardian reporter Jon Swaine reported hearing gunfire, and tear gas being fired at protestors running away.
Images posted on Twitter showed vandals smashing the windows of a McDonald's restaurant. "#Ferguson very tense at command center tear gas fired search for people under way," wrote St Louis Post-Dispatch reporter David Carson.
The city has been enduring violence since a white police officer on August 9 shot dead Michael Brown, an 18-year-old unarmed black teenager.
Brown shot six times
Autopsy results released by the Brown family's lawyer showed the teen had been shot six times, twice in the head.
The New York Times reported that the autopsy by Dr. Michael Baden, a former New York City chief medical examiner, found that one of the bullets entered the top of Michael Brown's skull, suggesting that his head was bent forward when he suffered a fatal injury.
Brown was also shot four times in the right arm and that all the bullets were fired into his front.
The newspaper said the bullets did not appear to have come from very close range because there was no gunpowder on his body.
That determination could change if there were residue on Brown's clothing, which Baden did not examine, the newspaper said.
Some of the bullets entered and exited Brown several times, the newspaper said, including one that caused at least five wounds.
It said one shattered his right eye, went through his face, left through his jaw and re-entered his collarbone. The last two shots in the head would have stopped him in his tracks and were likely the last fired.
Baden told the newspaper Brown would not have survived even if he had been taken to a hospital immediately.
Molotov cocktails thrown
The news came as protests in Ferguson again turned to violence, as police tried to enforce a state-enforced curfew.
Police moved in after people in the crowd threw Molotov cocktails at officers, KMOV-TV reported. There were also reports of gunshots fired in the crowd.
"Once there was a shooting, police had to come in. That being said, I'm troubled by tweets I'm reading saying children were gassed. #Ferguson," wrote Antonio French, a local politician who has been working for days to calm the crowds.
A CNN reporter in Ferguson tweeted that shots had been fired at police, but other media reported that some "shots" heard were fireworks.
#CNN Producer Steven Kastenbaum confirms/witnessed shots were fired at police. Says both police and media had to hit the deck.— Kyung Lah (@KyungLahCNN) August 18, 2014
Report of shots fired has been cleared as fireworks, police say. #Ferguson— Ryan J. Reilly (@ryanjreilly) August 18, 2014
The protest, held near the site where Brown was killed, followed a much larger and peaceful march outside the Greater Grace Church in Ferguson earlier in the day honouring Brown.
Young people who had gathered outside the church held their hands in the air, paying homage to what some witnesses said was Brown's last gesture before being shot.
"I'm astonished at the reversal of the mood," civil rights activist Jesse Jackson told CNN, saying that the mood earlier in the day among Ferguson residents had been more constructive.
"We were marching peacefully towards the police station just wanting to bend down on our knees with our hands up and say to the police, 'our hands are up, don't shoot'. All of a sudden they turned around and started shooting," Lisha Williams, who was in the march, told CNN.
Williams insisted that there was no violence from the crowd towards police.
- AFP, AP