Sydney (AFP) - A 10-year-old autistic Filipino boy made an emotional plea Monday for permission to stay in Australia, as tens of thousands called for him not to be deported despite the potential cost of his condition.

Tyrone Sevilla, who arrived in Australia from the Philippines legally as a two-year-old with his mother Maria Sevilla, has written to Immigration Minister Peter Dutton asking to stay.

The letter, which reads: "Dear Mr Dutton, can I stay in Australia please... Tyrone," was the first one her son had written and probably the most important he would ever write, Maria said.

"With our help, he managed to sit down and write all those letters on the page. For him to sit down and do that, it's a different Tyrone," she told AFP.

Maria Sevilla said the letter showed her son, who does not normally communicate by speaking, understood the family's situation after they were denied visas due to the probable cost of providing for Tyrone's care.

"I think he knows what's going on," she said.

Maria, who has been in Australia since 2007 on a variety of visas, said she and her son had been denied permission to stay longer because they were labelled a "burden" to Australian taxpayers.

The Sevillas presented a petition, signed by more than 120,000 people, to Dutton's electoral office in Brisbane in the hope that the minister would give compassionate consideration to their cause.

"Today is make or break, whatever we do today will help with our case," Maria, a registered nurse who works in a Queensland hospital, told the Australian Broadcasting Corporation.

"Australia is our home. Because we have been here for nearly eight years and we've been assimilated in the community.

"Our immediate family are here, which is our support.... I have my work here and I can actually provide for Tyrone."

The family said Tyrone did not speak Filipino or have any close relatives remaining in the Philippines, with his grandmother, grandfather, uncle, aunt and cousins all living in the Australian city of Townsville.

- Call for common sense -

Dutton said the immigration department was preparing a report for him on the case, and in the meantime a bridging visa -- which typically covers a 28-day period -- would be issued for the mother and son.

"In this case we need to apply common sense," he told the ABC.

"We're a compassionate society and we want to help families in difficult situations."

"There's no fear that anybody is going to be deported, there will be a bridging visa which will be issued which is standard practice in these matters," he added.

Dutton stressed that such decisions were always hard and emotional, but the immigration department must consider the costs of conditions such as autism on the provision of services.

"It is a difficult area because we have thousands of applications... but we have to be sensible about the number to whom we should provide that support," he said.

Dutton said a decision would likely be made within weeks, and it would take into account the fact that Sevilla was employed and could look after her son.

Australia takes a hard line against asylum-seekers arriving by boat, refusing them resettlement in the country even if they are found to be refugees and sending them instead to Pacific states.

But Maria Sevilla, who said she pays tax and has private health insurance, said she was overwhelmed by the support she had received from the Australian community.

"I am hoping that he (the minister) will see that there are a lot of Australians that are really supporting us," she said.

"I am still hoping that we will have a positive outcome."