A Wellington nurse says further strikes have been building up, as understaffing in emergency departments worsens

More than 36-thousand Nurses' Organisation members are striking from 7am to 11pm today, and again on Thursday.

Health NZ says the action could disrupt treatment, services and care over the entire week - especially for patients with non-urgent needs.

But Hutt Valley nurse Nathan Clark says staff don't have the safe capacity to care for passengers as is.

He says no one has been able to produce figures on how many appointments and procedures have been cancelled because there aren't enough staff.