A suspect remains in custody as specialist officers continue to make enquiries at the scene more than 24 hours after the attack.
The assault took place in the Lon Helyg area shortly before 2pm on Thursday.
During the afternoon there was also a heavy police presence at Welshpool Hospital where one man received emergency treatment to his body before he was transferred by ambulance to the Royal Shrewsbury Hospital.
A spokesman for Dyfed Powys police said: "“The safety of all at the hospital was the priority, and officers cordoned off the site whilst an investigation commenced.”
Police said part of Lon Helyg in Newtown was also cordoned off.
"They have remained in place for specialist search officers to conduct enquiries," the spokesman added.
"A 60-year-old man arrested on suspicion of serious assault remains in police custody as enquiries continue.
"The male victim remains in hospital."
Police thanked the Lon Helyg community for its patience.
Officers are appealing to anyone who has information in respect of this incident to contact them, either online at orlo.uk/v7DA0, by emailing email@example.com, or by calling 101.
"If you are deaf, hard of hearing, or speech impaired text the non-emergency number on 07811 311 908. Alternatively, contact the independent charity Crimestoppers anonymously by calling 0800 555111, or visiting crimestoppers-uk.org. Quote reference: DP-20201126-149."