Three more teens have been charged with murder, as the homicide investigation into US student Kyle Whorrall's killing shifts to a prosecution phase

The 33-year-old was fatally attacked at a bus-stop in Auckland in April.

After searches in Kaikohe, Mount Wellington, and Manurewa this morning - two 18-year-olds and a 17-year-old were jointly charged with murder and aggravated robbery.

Police say six people have now been charged in relation to the death.

They say investigations are ongoing, but they believe they've identified those involved.