Lax security at Indonesian airports and support for Islamic State among extremists in the world's most populous Muslim nation could lead to more plane bombings, potentially targeting Australians, a terrorism expert has warned.

Professor Clive Williams, from the Australian National University's Centre for Military and Security Law, has warned it would not be too difficult for an unsophisticated explosive device to be planted on planes leaving Indonesian airports.

Two employees of Egypt's Sharm al-Sheikh airport have been detained for questioning over the crash of the Russian airliner last month that killed all 224 people aboard.

Egyptian security reportedly confirmed CCTV footage showed a baggage handler carrying a suitcase from an airport building to another man, who was loading luggage onto the doomed airliner from the runway.

"I think it's more likely that being copy-catted than the kind of attack done in Paris," Prof Williams told AAP on Wednesday.

"It could be a baggage handler is paid money to put what he's told is drugs on an aeroplane, not knowing it's explosives."

Prof Williams, who is also a member of the International Association of Bomb Technicians and Investigators, also pointed out that Australians are a target for Islamic State because of Australia's involvement in military action targeting the terror group in Syria and Iraq.

"There is an Islamic State affiliate in Indonesia, which is JAT, and it's possible they could get a baggage handler in Indonesia to do the same sort of thing.

"Of course Australians are a target because of our involvement in the U.S.-led coalition against Islamic State."

The warning from Prof Williams comes after the former commander of an elite Indonesian counter-terrorism unit, now a senior minister with the government in Jakarta, confirmed on Tuesday that security forces are closely monitoring more than 100 foreign fighters who have returned from battlefields in Syria and Iraq.

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