The elderly victim’s wife told the Tele the couple were too upset to speak in detail about the incident.

However, she said she was more shaken than her husband by the apparently random attack, and praised her “good neighbours” for their support.

Police were today carrying out door-to-door inquiries and scenes of crime officers conducted a detailed examination of the area.

Detective Inspector Bobby Dow said, “This was a seemingly unprovoked attack on an innocent, elderly gentleman answering his front door.

“He is very understandably upset, and our efforts today are focused on trying to establish exactly what the motive was.”

The culprit, who is believed to be in his mid-30s, is described by police as being approximately 5ft 10in and of stocky build. He was wearing dark clothing, including a balaclava.

After the doorstep scuffle, the attacker ran away in the direction of Charlotte Street. The pensioner’s injury was treated at Ninewells Hospital.

One female neighbour, who did not wish to be named, said she would be wary of opening her front door in the future.

She said, “I am going to look out the window to see who it is first. The whole thing is totally out of the blue. I don’t know whether it’s totally random or someone on drugs.”

She said the street was usually “very quiet” and added, “Even when there was a school at the top of the road we didn’t get any bother. The whole thing is really shocking.”

Another neighbour, who has lived in the street for 12 years, said he had been left “shocked” by the attack.

He said, “The first I heard of it was from a neighbour at about 6.15pm. He said not to answer the door because a guy up the road had been attacked by a ‘hoodie’.

“It’s a very quiet street, and everybody looks out for everybody else. The neighbours are very wary of strangers walking about or people who don’t seem to fit in on the street.”

Tayside Police said anyone with information on the incident should contact them on 0300 111 2222 or speak to any police officer.