Ambulances have been diverted from Canberra Hospital for the second time in two months due to a surge in patient numbers.

The partial bypass began at about midday yesterday and lasted until around 4pm.

Just last month the emergency department recorded a record number of patients but said there was no obvious cause for the increase.

Canberrans are being reminded that emergency departments are only for urgent treatment and patients should attend a walk-in clinic or visit their GP for other medical care.