About 150 commandos secured the airport in Dili on Thursday before the deployment of 1,300 troops to help to restore peace and order after weeks of unrest.
John Howard, the Australian prime minister, said the East Timor government was desperate for the Australian troops to arrive.
"It's quite clear the situation in Dili has deteriorated [today]," Howard told reporters in Canberra. "There are widespread reports of a very chaotic situation.
"Given the detriorating situation we will go ahead, without any conditionality, with the full deployment and the 1,300 [troops] will be in place in a very short order."
Howard said the warship HMAS Adelaide was already in Dili harbour. Local media said 200 troops were aboard.
The government of East Timor has been struggling to cope with clashes initially caused by the sacking of about half the army. Before Thursday, these had left at least six people dead in Dili.
The government asked for troops from Australia, New Zealand, Portugal and Malaysia this week after a police unit rebelled and its own forces proved incapable of calming the situation.
Malaysian troops were also on their way to Dili on Thursday.
Malaysia will deploy 275 para-commandos, an army official told Reuters. The group would leave late on Thursday using C-130 Hercules aircraft.
They would be part of an eventual total Malaysian force of 500 men, comprising the military and police.
The Portuguese government said it would send 120 military police.
The arrival of Australian troops came amid reports of widespread shooting in the capital on Thursday.
Arlindo Marcal, East Timor ambassador in Jakarta, said: "According to the information that we have received, there have been victims, injured and killed. I cannot confirm the numbers yet."
Clashes started after about half
the army was sacked
Earlier reports said gun battles in the capital had killed at least three combatants and injured 14.
The army said that Domingos Kaykery Oliveira, an army captain, was shot and killed early on Thursday.
Letnan Gastao Salsinha, a spokesman for the dismissed soldiers, said two rebels had also been killed and 14 wounded.
At least five people have been killed and 22 injured in unrest in the capital this week, prompting the government to ask for international troops only days after celebrating East Timor's fourth anniversary of independence from Indonesia.