A bus driver was knocked out after being punched yesterday while on board his bus in Customs St West, Auckland.

A police spokeswoman said officers attended the incident around 1.40pm and the driver regained consciousness before being taken to an Auckland A&E clinic in a moderate condition.

The offender, who was not harmed, ran off before police arrived and inquiries were continuing, she said.

It was unclear whether the offender was a passenger on the bus or what provoked the assault, the spokeswoman said.