Detectives urged campers to come forward with any information
A man has suffered "horrific" multiple stab wounds and another has died at Scotland's biggest music festival.
A 22-year-old man was attacked at the T in the Park campsite at about 0045 BST. In a separate incident another man was found dead in his tent on Sunday.
About 80,000 music fans are at the three-day event, being staged in Perth and Kinross.
Tayside Police said they were looking for two men in connection with the attack.
The 22-year-old was assaulted in the festival camp site's "blue zone four" area. He is in a serious but stable condition.
The area where the incident took place was cordoned off for forensic investigation and officers have been interviewing witnesses and other festival-goers.
Det Ch Insp Bruce Kerr said: "This has been a horrific assault on a 22-year-old man who sustained multiple stab wounds."
He added: "It was a very serious incident where a camper was seriously assaulted and stabbed numerous times in the head and body.
"We're urgently trying to trace the males responsible and we're asking any campers or visitors to T in the Park, if they come across a blood-stained knife or similar weapon please leave it and contact any police officer or any steward right away.
"It's very important we do that because we still haven't found the weapon yet."
Det Ch Insp Kerr also said that the attackers were likely to have had blood-stained clothing.
It is understood the victim was attacked after trying to break up an altercation on the campsite and was found injured near a hedge separating the blue and yellow camp areas.
The detective said he may have died had it not been for the on-site doctor.
The victim, whose parents have been told about the attack, was taken to the intensive care unit at Ninewells Hospital in Dundee.
T in the Park event manager Colin Rodger said: "We are upset this incident took place, but we are extremely pleased to hear the assaulted man is in a stable condition.
"This is a real testament to the first class response from the emergency services that isolated the incident extremely quickly and provided the very best medical care anywhere in the country."
The first suspect was described as white, in his late teens, about 6ft 1in, of skinny build with short, dark brown hair and wearing a white tracksuit top.
The second was also said to be white, about 5ft 8in and of medium build and with short, dark brown "mullet-style" hair. He was wearing a red tracksuit top.
Before the stabbing, police said there had been no reports of serious crime at the festival site and just seven people had been taken into custody since Friday.
In the other incident, a 32-year-old man, who has not been named, was found by friends in his tent at about 1150 BST on Sunday and was later pronounced dead at the festival's on-site hospital.
Police said the cause of death was yet to be confirmed, but added that there were no suspicious circumstances.
T in the Park will end on Sunday night when US giants REM and dance veterans The Prodigy take to the stage.
In all, about 180 artists will have performed on 11 stages across the weekend.
Also performing on Sunday will be Primal Scream and Amy Winehouse.