FERGUSON: Police said Wednesday they had arrested 47 people as tensions rose after an otherwise peaceful night of protests in Ferguson, the Missouri town rocked by violence over the police shooting of an unarmed black teenager.

Three guns were seized in the latest protest rally in Ferguson, which has become ground zero of a new national debate on police treatment of minorities after Michael Brown, 18, was shot August 9 by a white police officer.

Captain Ron Johnson of the Missouri Highway Patrol said protesters threw glass and plastic bottles of water and urine at police towards the end of Tuesday night's protest, prompting officers to intervene and make the arrests.

Johnson stressed that unlike a violent protest Monday night, this time protesters did not fire guns at police and officers refrained from using tear gas to break up the rally.

“Tonight we saw a different dynamic,” he said.

He attributed this to a concerted effort by community leaders, activists and clergy to keep the rally peaceful and prevent it from being taken over by what he described as violent “agitators”.

Fears that the fatal police shooting of a knife-wielding black man might renew tensions failed to materialize, after successive nights of clashes with police in Ferguson.

“Hands up, don't shoot!” protesters chanted, holding their hands in the air in what has become the signature slogan of Ferguson's frustration with its overwhelmingly white police department.

US Attorney General Eric Holder is to visit Ferguson on Wednesday amid an ongoing federal investigation into possible civil rights violations.

A grand jury is meanwhile to begin Wednesday hearing witnesses to Brown's killing, amid calls for the police officer, Darren Wilson, to be put on trial for murder.

Meanwhile Brown's family was preparing for his funeral, which their lawyer said would take place on Monday.

'Criminal elements'

In contrast to previous nights, rather than firing tear gas head-on into the crowd, police with riot shields and armored vehicles kept a lower profile.

They finally intervened around midnight (local time), pushing the remaining crowd towards a newly designated public assembly area in a former car dealership.

Mingling with citizens at the outset of the march, who insisted on their right to protest, Johnson -- who is black and charged with restoring order in this mainly black town of 21,000 -- denounced what he called “criminal elements” who, after dark on Sunday and Monday, had ignored police orders to disperse.

“Cowards hide in the dark, and it's time for that to stop,” he told reporters.

Earlier Tuesday, a few miles (kilometers) away in St. Louis, officers shot dead an agitated man who yelled “kill me now” as he rushed at them with a knife during an apparent convenience store robbery.

St. Louis Metropolitan Police 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. “

Brown family seeks murder charge

Police have identified the white police officer who shot Brown in broad daylight on a residential street as Darren Wilson, 28, a police officer for six years.

Brown's family wants Wilson -- who reportedly has been granted leave from his duties -- charged with murder for “executing” their son.

In an op-ed column in the St Louis Post-Dispatch newspaper Wednesday, Holder pledged what he called a full, fair and independent investigation.

“And beyond the investigation itself, we will work with the police, civil rights leaders, and members of the public to ensure that this tragedy can give rise to new understanding - and robust action - aimed at bridging persistent gaps between law enforcement officials and the communities we serve,” he said.

Police contend that Brown was rushing at the officer, but other witnesses say the teenager -- who was about to start vocational college -- had his hands up, ready to surrender.

Brown was fatally shot less than half an hour after the theft of a box of cigars from a liquor store. Police named Brown on Friday as the suspect in that case, taking local anger to a new level.

A forensic pathologist retained by Brown's family said that the teen was shot at least six times -- twice in the head.

Three separate autopsies of Brown's remains are taking place -- by local authorities, by the family and by the Justice Department.

Federal law enforcement officials said that a military medical examiner who conducted the federal autopsy also concluded that Brown had six gunshot wounds, The Los Angeles Times reported, citing an unnamed government source.

US National Guard troops have been deployed to Ferguson to help control the unrest, amid criticism of the distrusted local force's handling of the protests, with even President Barack Obama saying there was no excuse for local police to use “excessive force. “But their role so far has been limited to guarding a command post in a shopping center away from the nightly protests.