The US attorney general is to travel to the riot-hit town of Ferguson, as the federal authorities step up efforts to restore calm after the fatal police shooting of an unarmed black teenager.

Eric Holder will go to the town on Wednesday to meet officials in charge of a federal investigation into the killing of Michael Brown on 9 August.

President Barack Obama urged the local community to "try to unite each other".

Police fired tear gas amid a tense stand-off with protesters.

Footage showed the police arresting several protesters, as lines of armed officers faced up to crowds of protesters.

A photographer working for Getty Images agency was among those arrested, though he was freed after a few hours.

The National Guard has been deployed to support police operations, and Missouri Governor Jay Nixon on Monday lifted a night-time curfew in the town.

Although the town appeared tense and there were localised flare-ups, the protests were generally peaceful.

"I realise there is tremendous interest in the facts of the incident that led to Michael Brown's death, but I ask for the public patience as we conduct this investigation," Mr Holder said.

And he stressed that the investigation into the shooting of 18-year-old Mr Brown was "a critical step in restoring trust between law enforcement and the community, not just in Ferguson, but beyond".

Separately, President Obama said he understood the "passions and anger" provoked by the death of the teenager.

But he said giving into anger "by looting or carrying guns and even attacking the police only serves to raise tensions and stir chaos".

"It undermines rather than advances justice," he said.

(BBC)