Australian Prime Minister Tony Abbott on Wednesday bowed to pressure to increase refugee numbers in the face of the Middle East crisis and confirmed Canberra will also join U.S.-led air strikes on the Islamic State group in Syria.

With his hardline against asylum-seekers under intense scrutiny given the drama unfolding in Europe, Abbott said the government was acting "with our head as well as with our heart" to help the thousands of migrants fleeing the conflict.

A Melbourne man has been charged with attempting to leave for Iraq to fight with Kurdish forces against the Islamic State group, just weeks after another Australian was killed during a similar venture.

Jamie Williams, 28, is accused of preparing to enter a foreign country with the intention of engaging in hostile activities -- which carries a maximum penalty of life imprisonment.

The mother-in-law of a notorious Lebanese-Australian Islamic State group fighter said Monday she was "devastated" that police had refused to help bring her five grandchildren home from Syria.

Karen Nettleton's daughter Tara is married to Khaled Sharrouf, who gained global infamy last year when he posted pictures of himself and his seven-year-old son on Twitter holding up the severed heads of soldiers.

Australia's domestic spy agency Thursday played down concerns that maps shown in a media briefing revealing the source of homegrown fighters travelling to the Middle East were classified, after fears their publication was a security breach.

The maps, which revealed the Sydney and Melbourne suburbs where fighters heading to join jihadists came from, were photographed and filmed by journalists during a meeting Wednesday between Prime Minister Tony Abbott and spy chief Duncan Lewis.

The mother-in-law of one of a Lebanese man and Australia's most notorious Islamic State fighters has pleaded for the government to help her "desperate" daughter and five grandchildren flee the Middle East, saying she made "the mistake of a lifetime.”

Karen Nettleton's emotional appeal for help came after reports that her son-in-law Khaled Sharrouf and his friend Mohamed Elomar were killed in fighting in the Iraqi city of Mosul in the past week, although officials Wednesday suggested they may have died in Syria .

Australian authorities work within the law to stop asylum-seeker boats, Prime Minister Tony Abbott insisted Tuesday after reports officials have made cash payments to members of people-smuggling rings for years.

The government has refused to deny reports that six Indonesian crew members were paid $US5,000 each to return an asylum-seeker vessel to Indonesia in late May, saying no comment will be made on operational issues.

Indonesia's vice president warned Monday that paying people-smugglers would amount to "bribery" after Australia was accused of handing out money to turn back a boatload of asylum-seekers.

Allegations that the captain and five crew of a boat, carrying migrants from Bangladesh, Myanmar and Sri Lanka, were each paid US$5,000 by an Australian immigration official to turn back to Indonesia were made to police on Rote island in the country's east last week.

Prime Minister Tony Abbott said Friday Australia would do "whatever we need to do" to combat people-smuggling as he repeatedly refused to deny claims an official paid thousands of dollars to turn back a boat from Indonesia.

Indonesian authorities said they were investigating allegations told to local police that the captain and five crew of a boat carrying asylum-seekers were each paid US$5,000 by an Australian immigration official to return to the Southeast Asian nation.

Cambodia received its first batch of asylum-seekers from Australian custody on Thursday, with rights groups labeling them "human guinea pigs" for an uncaring policy by Canberra to offload refugees onto other countries.

The migrants -- three Iranians and one ethnic Rohingya from Myanmar -- were flown into Phnom Penh, the capital of one of Southeast Asia's poorest nations with a weak record of upholding human rights.

Australia hit back Friday at criticism of its response to thousands of migrants stranded at sea in Southeast Asia, saying it was generous towards refugees in the region.

When asked Thursday whether Australia would offer to resettle the migrants from Bangladesh and Myanmar's oppressed Rohingya minority, Prime Minister Tony Abbott replied, "nope, nope, nope".