HUNDREDS of operations are being cancelled and patients refused clinical care during rolling industrial action by nurses.

By yesterday afternoon 217 beds were closed in 22 hospitals across NSW, with more closures expected overnight and today.

Nurses at one of Sydney's biggest hospitals yesterday voted to close scores of beds as their fight to secure new minimum staffing levels escalated.

The closures at Westmead Hospital will start at 7am today, affecting non-emergency surgery, outpatients and other clinical and diagnostic care. Nurses also voted for similar closures at St George Hospital in Sydney's south, which has about 600 beds.

The NSW Nurses' Association said more action is likely at Nepean Hospital and in Newcastle and Tamworth.