Cyber criminals hacked a medical practice and stole patients' confidential information in a terrifying security breach.

Perth Anaesthetic Group in the city's south was hacked on Thursday morning and criminals gained access into the hospital's database.

The cyber hackers sent out fake invoices to several patients demanding they submit payments for treatments.

Perth Anaesthetic Group in the city's south was hacked on Thursday with patients receiving fake invoices demanding payments (pictured: Southbank Day Surgery where Perth Anaesthetic Group is inside)

Jane McGrath, the manager of the group, said the cyber attack was recognised within minutes.

'The breach was controlled and the impacted individuals have been contacted,' Ms McGrath told The West Australian.

'There was no ransom demand and no money was paid.'

In the wake of the attack an email was sent around to patients of the group ensuring them that security on the hospital had been increased.

Andrew Miller, Western Australia President for the Australian Medical Association said 'sensitive information' on patients had been on offer to the hackers.

'There's no doubt potentially quite sensitive information here,' he said.

'We tell our people this is the world we're living in and you can't trust any email attachment and need to be very suspicious of all stuff that comes in. We have to continually update our approach and services to stay ahead of it.'