The ongoing bushfire crisis in Australia has forced Prime Minister Scott Morrison to cancel official trips to India and Japan planned for the second half of January.

The Australian leader is under intense pressure at home over his handling of the emergency, having flown to Hawaii for a family holiday in December with fires raging, and has faced criticism over government's environmental policies and stance on climate change.

Morrison said in a briefing on Saturday that he had spoken to Indian Prime Minister Narendra Modi and Japan's ambassador to Australia, Reiichiro Takahashi, seeking to reschedule the planned meetings.

"I should stress that both of those scheduled meetings are postponed and will move quickly to identify another opportunity," he told reporters.

Morrison also revealed a big step-up in the military's role in tackling the bushfire crisis, announcing that he had called up 3,000 military reserves to tackle a crisis that began in September. 

"Today's decision puts more boots on the ground, puts more planes in the sky, puts more ships at sea," he said.

A two-star general has also been appointed to oversee the military's response to the crisis and helicopter carrier HMAS Adelaide has been deployed to help the bushfire effort.

The announcement came after weeks of criticism targeted at Morrison over his decision to go on an unannounced holiday to Hawaii, refusal to raise emissions targets or curb coal exports.

Morrison cut short the Hawaii trip and apologized, but fueled the criticism by telling a radio station: "I know Australians understand this and they'll be pleased I'm coming back, I'm sure, but they know I don't hold a hose, I don't sit in a control room."

The prime minister has defended his handling of the crisis and sought to play down the significance of heckling against him in bushfire-hit communities.

A tearful pregnant woman and a volunteer firefighter refused to shake his hand and other residents peppered him with verbal abuse and suggested, colorfully, that he leave. 

"People in these situations have a mix of emotions," Morrison said. "These arms have given a lot of hugs."

Australian firefighters continue to battle dangerous conditions, with fires in New South Wales and Victoria states expected to burn uncontrollably in temperatures above 40 degrees Celsius and strong, shifting winds threatening to fan and spread the flames.

Bushfires have killed 23 people and destroyed more than 1,500 homes since September, Morrison confirmed on Saturday.

(With input from agencies)