Police say a 73-year-old man has been found dead following a muti-agency search that ran over the weekend.

A police spokesperson said they found a body in the Namoi River at Walgett near Marjorie Phyllis Walford Bridge at about 9:30am today (Monday 22 September.

Authorities launched the search last week after he was last seen leaving a Walgett medical facility on Friday evening 19 September at around 9.45pm.

A geo-targeted alert was issued on Saturday 20 September to smartphones within Walgett and surrounding areas, while the police air branch (PolAir) SES, the Rural Fire Service VRA Rescue took part in an "extensive" search in the river and surrounding areas.

Family and friends held fears for the man given his age and dementia.

"While the body is yet to be formally identified, it is believed to be that of the missing man," the police spokesperson said.

A report will be prepared for the information of the Coroner.