A man working as an Uber driver admits to the fatal weekend shootings of six people in Kalamazoo, Michigan, a police detective testifies in a case raising questions about how the car service vets its drivers.

A man arrested on suspicion of shooting dead six people in the northern US state of Michigan is an Uber driver who may have picked up fares during the killing spree.

Six people are shot and killed and several others wounded in Michigan, US in a series of apparently random shootings, authorities say.