A man has fled on a bike after an aggravated robbery at a Christchurch petrol station.

The man threatened employees with a knife and demanded cash at Mobil Woolston at 10pm yesterday, police said.

It was not known how much money was taken.

A 47-year-old man appeared in the Christchurch District Court last week, accused of using a bike to get away after robbing two Kiwibank branches in Riccarton.