Police used smoke and tear gas to enforce a curfew on protesters early yesterday morning in Ferguson, Missouri, where an unarmed black teenager was killed by police last week.

Seven people were arrested during the night in the St Louis suburb. Campaign group More claimed that all seven were arrested after being “dragged out of cars, some parked in their own driveways.”

Police swarmed the mainly black area in armoured vehicles shortly after the curfew started, claiming they were responding to reports of a break-in rather than seeking to enforce the dispersal order.

Hundreds of protesters left peacefully before the curfew took effect but many refused, chanting: “No justice! No curfew!”

The crowd bellowed: “We have the right to assemble peacefully” as officers began putting on gas masks.

A man was shot and critically injured during the night and a police car came under fire.

Police had appeared to back down from the combative approach they took immediately after the shooting that led to running battles between riot police and protesters.

But tensions flared again on Friday night after police revealed that the officer who shot 18-year-old Michael Brown was Darren Wilson, a white officer, and Governor Jay Nixon declared a state of emergency in Ferguson on Saturday.

They also released subsequently disputed CCTV footage alleging that Mr Brown had robbed a corner shop shortly before he was shot — although Mr Wilson didn’t know that at the time.