An elderly man had his front teeth smashed by raiders who then struck at the homes of two other pensioners.
Still shaken by his ordeal, Robert Steele, 78, said: "They really were brutes and I hope the police catch them."
The same robbers later attacked an 80-year-old man and threatened a 71-year-old woman.
Mr Steele said: "I would have given them the money. There was no need for violence."
He was expecting a visitor at his home in Freehold Terrace, Hollingdean, Brighton, when he answered a knock at the door.
He said: "Two men pushed me sideways and said they were looking for a pipe leak.
"I thought that was a likely story and then they forced me into my bedroom.
"The bigger of the two punched me in the face, knocking out my two front teeth.
"He hit me on the head with a torch and threatened me. He demanded a fiver and when I got my wallet, he grabbed it and took all my pension money.
"He held me down on my bed with his arm round my throat while the other man ransacked the place, pulling out drawers and opening cupboards looking for money.
"As soon as they left, I rang the police who were here straight away."
Retired film cameraman Mr Steele added: "I warn all elderly people to keep their doors shut and not let anyone in they don't know."
The attack happened on Tuesday at 5.45pm. Just 15 minutes later, a woman was robbed in her home in Middleton Rise, Coldean.
Two men kicked their way through the front door and threatened her as she sat terrified in her lounge. She handed over cash before the men ransacked her home.
A short while later, another elderly man was robbed at his home in Bevendean Crescent, Moulsecoomb, Brighton.
He tried to defend himself with his walking stick but was overpowered.
Police are linking all three robberies.
Detective Inspector Paul Fullwood, heading Operation Edinburgh, said: "All of these victims are elderly and extremely vulnerable and the unnecessary violence used by the robbers sickens me.
"I want to appeal to the criminal fraternity in the city to come forward and help us catch these men."
Police have stepped up patrols on all three estates and officers were last night carrying out house-to-house inquiries.
Police are looking for two men, both white.
One is in his 20s, 6ft 1in, of large build with short, light-coloured hair.
The other is 5ft 2in, in his late teens or early 20s, slim with short hair.
Witnesses or anyone with information should contact Brighton CID on 0845 6070999 or Crimestoppers on 0800 555111.
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