A major police investigation was launched today in a bid to track down the attacker, who was apparently seen prowling the hospital grounds prior to the incident.

The 40-year-old nurse was not seriously injured, but both her and her colleagues were described as “badly shaken”.

A statement released by Tayside Police gave details of the attack.

“We are carrying out extensive inquiries in and around PRI after a female member of the nursing team was attacked while working in a busy ward about midnight,” it said.

“The attacker may have been prowling for some time and may have been seen acting suspiciously near the hospital on Wednesday.”

The assailant is described as a white male, aged 25 to 30, between 5ft 10in and 6ft, of slim build and with gaunt features.

His hair is brown and cropped and he was wearing a dark, Tammy-type hat with a lighter horizontal band, a dark, waist-length zipper top, light blue jeans and white trainers.

He may have a tattoo on the right side of his neck, as well as tattoos on his knuckles, and may be missing front teeth.

Detective Inspector Colin MacKay is leading the hunt to catch the attacker.

“It is vital we catch the man responsible as soon as possible and I would appeal to anyone who has information to contact police immediately.”

Police added it was possible the suspect was drinking in Perth city centre late on Thursday evening.

Anyone who may have seen a man acting suspiciously in or around the hospital, or on nearby streets on Wednesday or Thursday evening, is asked to contact police in Perth on 01738 621141.

An NHS Tayside spokesperson said they had been advised by police not to make any comment on the attack and were today referring all associated calls to the Tayside force.

Today there was some consternation among nurses arriving at PRI. One nurse said, “This sounds like a pretty serious incident. There have been assaults in the past from people being treated, especially in A&E, but I have never heard of an incident involving an intruder. It is shocking and a worrying development for all staff.”

Meanwhile, Colin Poolman, regional officer with the Royal College Of Nursing, said his organisation was “extremely concerned” by the attack.

“We are calling on the Trust to review their security arrangements as a matter of urgency,” he said.

“This is another dreadful illustration of how vulnerable nurses are. Everything possible needs to be done to ensure the safety of all staff throughout the NHS.”

A spokesperson for NHS Tayside said, “The safety of all staff is paramount and we are viewing this incident as a matter of utmost importance.

“We are carrying out our own investigation and, as part of this, we will be reviewing our security measures. We try to ensure all our premises are as secure as possible while still being accessible to the public.”