Police saturate roads to prevent further fatalities as national holiday road toll stands at six

The road toll for Australia's holiday season has risen to six, leaving families mourning on Christmas Day.

A man died after his 4WD crashed into a bus, injuring a woman and a child, on a highway northwest of Toowoomba in Queensland yesterday.

The car's passengers suffered abdominal injuries and were taken to Toowoomba Hospital where they remain in a stable condition.

The coach's 18 elderly passengers and the driver all escaped serious injury.

In regional Victoria, a woman died after a car flipped when the driver lost control on the South Gippsland Highway near Koonwarra yesterday morning.

The woman, who was a passenger, died at the scene while the male driver, aged in his 20s, was taken to hospital with minor injuries.

Another woman died after her car collided with a B-double truck on South Australia's Sturt Highway on Wednesday morning.

The 72-year-old woman from Victoria was taken to Royal Adelaide Hospital but died that night as a result of her injuries. 

Three others also died on Wednesday.

A passenger died in a two-car crash on the Bruce Highway, about 20km north of Gin Gin in central Queensland, about 12.45pm.

A motorcyclist aged in his 20s was killed hours later after he collided with a taxi in Albert Park, in Melbourne's inner south.

Police believe the taxi was doing a U-turn when the man crashed into it just before 5pm.

Another man later died in Tasmania after his car collided with a vehicle travelling in the opposite direction south of Somerset.

Police around Australia have increased safety operations over the Christmas period, including stepping up drug and alcohol testing.

*The national road toll period runs from 0001 December 23, 2015 until 2359 January 3, 2016, local times.