Protests in Ferguson, Missouri, turned violent, with some people lobbing Molotov cocktails and other objects at police who responded with smoke bombs and tear gas to disperse the crowd.

The suburb of St Louis has been rocked by racial unrest since a white police officer shot and killed 18-year-old Michael Brown, an unarmed black teenager.

The situation became tense after nightfall, with police ordering people to go home and then using smoke bombs and later tear gas after some people threw Molotov cocktails and other things at them.

Two reporters said they were detained by police. Wesley Lowery of The Washington Post and Ryan Reilly of The Huffington Post said they were handcuffed and put into a police van after officers came in to quickly clear the fast-food restaurant where they had been doing some work.

A video filmed at the scene shows how Al-Jazeera journalists covering the riots got caught in a cloud of tear gas.

Ferguson Police Chief Thomas Jackson said investigation of the shooting could take weeks to complete. In the meantime he welcomes Justice Department training on racial relations in the suburb, where two-thirds of the 21,000 residents are black, while all but three of the police force's 53 officers are white.

Jackson has faced mounting demands from protesters, clergy and even hackers to reveal the identity of the officer who shot Brown. Jackson argues that revealing that detail could bring retribution to the officer.

Police have said Brown was shot after an officer encountered him and another man on the street. They say one of the men pushed the officer into his squad car, then physically assaulted him in the vehicle and struggled with the officer over the officer's weapon. At least one shot was fired inside the car. The struggle then spilled onto the street, where Brown was shot multiple times.

Dorian Johnson, who says he was with Brown when the shooting happened, has told a much different story. He has told media outlets that the officer ordered them out of the street, then tried to open his door so close to the men that it "ricocheted" back, apparently upsetting the officer. Johnson says the officer grabbed his friend's neck, then tried to pull him into the car before brandishing his weapon and firing. He says Brown started to run and the officer pursued him, firing multiple times. Johnson and another witness both say Brown was on the street with his hands raised when the officer fired at him repeatedly.

The notorious hacking collective, Anonymous, has taken credit for burrowing into the city website and shutting it down for much of Monday. The group also released what it said were audio excerpts from St Louis County dispatch on the day Brown was killed. Police declined to comment on the recordings.

Some civil rights leaders have drawn comparisons between Brown's death and that of 17-year-old Trayvon Martin, who was fatally shot by a Florida neighbourhood watch volunteer who was later acquitted of murder charges.

The case has provoked a broad discussion on social media sites about the death of young black men in racially tinged shootings. On Twitter, a campaign using the hashtag #IfTheyGunnedMeDown prompted many black users to post photos of themselves and ask how they might be portrayed in news reports if they became shooting victims.

People on the scene have tweeted photos of what appear to be unexploded flash grenades and rubber bullet wounds, while others have drawn comparisons between what is happening in Ferguson with the civil rights protests 50 years ago and with what is happening in Palestine today.