A man has had his therapy dog stolen during an armed robbery at Reservoir.

The 43-year-old was taking his American staffy, Alabama, for a walk with his carer along Palm Avenue just after 9pm on Saturday night, when he was approached by three people armed with a knife, who demanded cash before taking his dog.

His carer, Marco, told Neil Mitchell he tried to stop them.

Press PLAY below to hear what happened

There were no physical injuries during the incident.

Any witnesses or anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au