Michael Brown’s parents have filed a wrongful-death lawsuit against the city of Ferguson opening a new chapter in the legal battle over the 18-year-old’s fatal shooting by a white officer that sparked a protest movement about the way police in the US treat black people.

The parents of the black teenager gunned down by police in Ferguson, Missouri, have rejected an apology by the city's top cop, saying he should be sacked and the white officer who shot their son arrested.