The death of another black teenager by police gunfire in the heart of Missouri has sparked fresh protests following months of unrest about alleged police racism.

18-year-old Toni Martin was last night shot dead by a police officer in front of a Mobil gas station in the St Louis suburb Berkeley after reportedly threatening him with a gun.

St Louis police spokesman Sgt Brian Schellman said that Martin drew a gun and pointed it at the officer who, "fearing for his life", fired several times.

Police claim Martin's gun has been recovered at the scene.

There was a second man with Martin who fled, according to the statement.

Footage of the build-up to the shooting has been released on YouTube by St Louis police, which they claim shows a suspect pointing a gun at the officer.

The gas station at which Martin died is only five miles west of Ferguson, Missouri where a police officer killed black teenager Michael Brown in August - an incident that led to rioting.

Although reports that Martin was armed may separate this case from those of Brown, Eric Garner and Tamir Rice, recent racial tensions in the US led to impromptu anti-police protests.

A crowd of around 100 people arrived at the scene, with livestreams showing protesters confronting police officers, shouting accusations and insults.

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Unconfirmed reports say multiple arrests have been made and one person tasered.

Minor damage was done to shops and cars in the surrounding area in the aftermath of the shooting.

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Local journalist Andrew Westmoreland tweeted: "Police suiting up in riot gear now at #AntonioMartin shooting site."

One altercation between police and protesters in which someone hurled a firework into a crowd has been caught on film.

Pictures and videos of protests are being posted on Twitter, where there is huge activity under the hashtag #AntonioMartin.

Some users have claimed that Martin was lying on the ground for a period of time - between 30 minutes and two hours - before emergency services arrived.

There is footage of Martin's mother, devastated at the news of his death, wrestling police to attend to his body. She was also filmed saying: "They started shooting. That's my baby."

Martin's mother told local news outlets that he had just left to visit his girlfriend, and said to NBC that she did not think Martin was armed.

There are, as well, users spreading misinformation.

One user, who spoke to The Huffington Post and was sourced by The Independent in an earlier version of this article, falsely claimed to be Martin's "best friend" and present at the time of his shooting.

The St Louis police will detail the incident at a press conference shortly.