UPDATE: Police are speaking to the driver of a ute that hit and killed a man on Kwinana Freeway early Thursday morning.

The freeway reopened at about 9.15am after northbound lanes between Leach Highway and Mill Point Road were closed during peak hour as police investigated the death.

A police spokesperson confirmed a white four-wheel drive ute hit the 29-year-old man as he was walking in the freeway near Canning Highway at 5.15am.

The driver of the ute is assisting detectives from the major crash squad with their investigation.

Traffic remains heavy heading into the city and motorists are urged to take alternative routes at Leach Highway, Canning Highway, Stirling Highway and Albany Highway.

Detectives wish to speak to anyone who may have witnessed or have dashcam video of the crash.

Anyone with information can call Crime Stoppers on 180 333 000 or make a report online.