An asylum seeker has been charged with making a bomb threat on a plane taking him from Perth to the Christmas Island detention centre.

It is alleged a 27-year-old Lebanese national threatened to blow up the chartered jet which was transporting him and other asylum seekers last Thursday.

The Australian Federal Police say he has been charged with making a false threat.

He briefly appeared in court yesterday and will reappear on March 10.

It comes amid reports of building tensions among the more than 2,000 asylum seekers inside the Christmas Island centre.

Several sources have told the ABC that what they call a "substantial" hunger strike is underway and about six detainees have sewn their lips together.

It is understood they are protesting against conditions inside the detention centre.

Greens immigration spokeswoman Sarah Hanson-Young says tensions are rising because asylum seekers are being held in detention for far too long.

"Sources inside are telling me there's a large number of people on hunger strike including a handful of people who've disturbingly sewn their lips together," she said.

"This is a reminder of the horror days of what used to happen under the last Coalition government; very vulnerable people pushed to their absolute breaking point."

Senior government minister Kevin Andrews, who has previously held the immigration portfolio, says it is regrettable asylum seekers are reportedly harming themselves.

"Any sort of self harm is to be regretted wherever it happens and we'd hope those sort of actions don't continue into the future," he said.

Immigration Minister Scott Morrison has declined to confirm or comment on the reports of the protest.