Notorious backpacker serial killer Ivan Milat has been transported from his cell in Goulburn's supermax prison to a public hospital in Sydney, where he is undergoing tests.

A spokeswoman for Corrective Services confirmed that a 74-year-old inmate is currently being treated at a Sydney hospital.

Ivan Milat in 1998. Credit:Darren Pateman

The Sydney Morning Herald has confirmed Milat was checked in to a secure, inmate-only annexe at Prince of Wales Hospital in Randwick on Monday afternoon, where he is to undergo a diagnostic procedure.

NSW Corrective Services Commissioner Peter Severin told Seven News the annexe is jointly staffed by Corrective Services NSW and NSW Health.

"We've made very strong security arrangements for that, we've got specialist teams to ensure that at any time there is absolute guarantee of safety and security," Commissioner Severin said.

Milat was jailed in 1996 and is serving seven life sentences for the brutal murders of seven backpackers whose bodies were dumped in the Belanglo State Forest between 1989 and 1993.

His condition is not currently life-threatening, and he is expected to return to prison in a matter of days.