POLICE in Ferguson, Missouri, have fired tear gas, stun grenades and smoke bombs to disperse 350 protesters, the fourth night of racially charged demonstrations after police shot to death an unarmed black teenager.

Some demonstrators hurled rocks at police as others scattered, while smoke engulfed the area. Two young men were seen preparing what looked like petrol bombs in a bus-stop shelter, their faces covered by bandanas. Police said protesters had thrown petrol bombs at officers.

Protesters have gathered every night since Saturday when 18-year-old Michael Brown was shot to death in the mostly black suburb of St Louis, during what authorities said was a struggle over a gun in a police car. Some witnesses say he was outside the car with his hands up.

Loading article content

Police have deployed camouflage-clad officers in body armour, including one manning a rifle on top of an armoured car.

President Barack Obama has called for a peaceful response to the shooting.