Justice officials say the 29-year-old Turkish biker was nearing the end of a prison sentence at Hirtenberg jail in Lower Austria, and had been granted unsupervised day release.
A police unit tried to stop the 29-year-old at around 6pm in Floridsdorf when they noticed he was riding an unlicensed motorbike. He refused to pull over and they gave chase, calling for reinforcements.
As the biker headed towards Strebersdorf a police officer who was manning a pedestrian crossing to make sure schoolchildren could cross safely tried to flag him down and stepped into the road.
After initially slowing down, the biker then increased his speed, knocking the officer down and falling off the bike himself. The police officer was taken to hospital by helicopter and is in a critical condition. The motorcyclist was also injured and is being treated in hospital but police say they will question him on Friday.
Police spokesman Roman Hahslinger said the man was carrying his younger brother's identity papers and was serving a six year sentence for drug and property crimes.
Brigadier Alfred Steinacher, director of Hirtenberg prison, said the man was not considered a risk to the public and had been granted day release as a reward for good behaviour. He left prison on Thursday morning and was due back on Friday morning, by 10am. Steinacher said the man had recently tested clean for drugs.
Police said the Yamaha motorbike belonged to a relative of the prisoner and was not licensed to be used on the roads - and that it had a provisional license plate made of cardboard.