A couple from Singapore was stabbed by an unidentified person near Akkagarla temple on the Alipiri-Tirumala pedestrian path in India, Malaysia Nanban reported.
The couple, who sustained injuries on their necks, was said to be stable.
The victims, Govinda Thyagarajan, 57, and his wife Latha, 50, arrived at the Bangalore International Airport late Tuesday night and reached Tirupati in Andhra Pradesh at 4am.
They began trekking the Tirumala Hills and when they reached near the Akkagarla temple, an unidentified youth attacked them with a knife.
After leaving the couple in a pool of blood, the youth ran away.
After hearing the screams of the couple, some of the trekkers rushed to the area and called for an ambulance.
Police said that the motive of the attack was not known as the assailant had not taken any of their valuables.
The couple were wearing jewellery and had about Rs2 lakh (S$4,139) with them.