Protests have been held in Ferguson in Missouri - a year after an unarmed black teenager was shot dead by a white police officer.

Michael Brown's death sparked weeks of riots - and raised questions about the state of race relations in America.

The officer responsible was cleared of any wrongdoing, but resigned in November.

4 and a half minutes of silence will be observed later to mark the four and a half hours his body lay face down on the pavement before it was taken away.

Michael Brown senior led the march, which started at a memorial on the site where his son was shot.