The prime minister is expected to visit Rural Fire Service headquarters over the weekend after flying into Sydney on Saturday.

Mr Morrison has defended his family holiday to Hawaii during the bushfire emergency, saying it was arranged some time ago.

But he has been criticised for going on leave as intense blazes burned across the country.

"I deeply regret any offence caused to any of the many Australians affected by the terrible bushfires by my taking leave with family at this time," Mr Morrison said on Friday.

"I have been receiving regular updates on the bushfires disaster as well as the status of the search for and treatment of the victims of the White Island tragedy."

Two volunteer firefighters were killed in a vehicle turnover near Buxton, south west of Sydney, on Thursday night.

"Given these most recent tragic events, I will be returning to Sydney from leave as soon as can be arranged," Mr Morrison said.

His wife and daughters will remain in Hawaii.

Australian Associated Press