The woman and her husband, Rama Krishna, had come to the city from Mahabubnagar district for medical consultations.
They had gone to relieve themselves near the river last night when a group of around five persons tried to molest the woman, police said.
When her husband objected, one of the miscreants allegedly attacked him with a blade several times before they escaped from the spot, police added.
"Following a complaint by the woman, we have booked a case under Section 307 (attempt to murder) and 509 (word, gesture or act intended to insult the modesty of a woman) of IPC.
Rama Krishna has been shifted to a hospital and is undergoing treatment, police said.