Around 30 police officers are searching woodlands after a possible sighting of a prisoner on the run.
Tayside Police warned the public not to approach Lee Cyrus, 47, who disappeared on day release from North Sea Camp open prison in Boston, Lincolnshire, earlier this month. He is serving a life sentence for robbery.
Police are investigating two violent attacks in the Perth area in the last fortnight, including the sexual assault of a woman by an intruder who attacked the victim in her own bed.
Police said a "suspicious" male was spotted by an off-duty officer by the A90 Perth to Dundee road. He lost sight of the man when he ran into woods at Kinnoull Hill. Specialist search officers and dogs have been hunting the area.
A police spokeswoman said: "The public will be aware that Tayside Police, along with other forces, are making enquiries to trace the whereabouts of absconder Lee Cyrus. It is too early to confirm whether today's sighting is linked to those inquiries.
"In appealing to the public for any information they might have, we would urge people to be vigilant and not to approach this man but to contact the police immediately."
Cyrus, also known as Ivan Leach, failed to return to prison on Tuesday October 9 and police believe he may have travelled to the Tayside area.
The male spotted was described as being of medium build, with a round face and clean shaven. He wore muddy, dark-coloured waterproof trousers and top and a beanie hat. He was carrying a rucksack-style bag, police said.
Tayside Officers are investigating the sexual assault of a 23-year-old woman as she slept in her home in the Bridgend area of Perth.
The intruder threatened her before the attack at around midnight on Monday October 15. The assault followed a nearby robbery the previous night in which a woman was attacked in her home.