The men are patients at the Beatson Oncology Centre

The three men are patients at the Beatson Oncology Centre in Glasgow.

Part of the Beatson centre is sited at the city's Western Infirmary, where a ward was closed after four patients were hit by the superbug last week.

NHS Greater Glasgow said the cases were unconnected. It is not yet known whether the patients have contracted the same strain of MRSA.

A spokeswoman said the Beatson unit was in a different building to the hospital ward and the ward had reopened for admissions on Friday.

Health officials said cancer patients were more vulnerable to MRSA as their immune systems could be damaged by treatments designed to destroy cancer cells, such as chemotherapy and radiotherapy.

'Minimise infection'

With the exception of people who have received bone marrow transplants, cancer patients receiving long-term therapy were the most vulnerable of all to infection, officials said.

Dr Harry Burns, director of public health for NHS Greater Glasgow, said MRSA was now a worldwide problem.

"While it may never be fully eradicated, its impact can be reduced," he said.

"The NHS in Greater Glasgow is working extremely hard to minimise infection risks, and positive results over the past two quarters are already being achieved."

Two of the Beatson patients are receiving treatment and are said to be "stable".