Ottawa police have released several black and white photographs of the man they believe is behind the violent robbery of two taxi drivers.

The man in the photos is accused of taking a ride from taxi drivers from downtown's Rideau Street to Vanier and then -- at knifepoint -- demanding the drivers hand over cash when reaching his destination off Montreal road.

Police say this happened on two separate occasions.

The first time was on June 13 at 1:50 in the morning. No money was taken but the driver did receive a knife wound to his finger.

The second incident reportedly took place on June 14 just after midnight. This time the alleged robber made off with an undisclosed amount of cash and the taxi driver suffered cuts to his head and fingers.

Police describe the suspect as white, early 20s and between 5'6" and 5'8". Police say he has short hair and speaks English without an accent.

Anyone with information is asked to call the Robbery Unit at 613-236-1222 ext. 5116 or Crime Stoppers at 613-233-8477 (TIPS).