SYDNEY (AFP) - An asylum-seeker has been charged over an alleged incident on a flight to Australia's Christmas Island, the police said on Tuesday, with reports he claimed to have a bomb.

The incident came as a senator told Australian media that a "large number" of detainees on Christmas Island had launched a hunger strike, with some sewing their lips together in protest at the length of time they were being kept at an immigration centre there.

Australian Federal Police said Tuesday that a 27-year-old Lebanese man was charged under a section of the Crimes Act which relates to false threats or statements related to destroying, damaging or endangering an aircraft and those onboard.

The police "can confirm a referral was received on 9 January 2014 in relation to an alleged incident involving a Department of Immigration and Border Protection detainee on board a flight from Perth to Christmas Island", according to a statement.

"The detainee has been charged under the Crimes (Aviation) Act 1991."

The police would not elaborate further, but reports said the man had become upset while flying from Perth to Christmas Island, Australia's remote Indian Ocean territory which houses the country's main immigration processing centre.

The man made statements which worried staff, including that he had a bomb, The Australian newspaper said, although it added that those familiar with the case said it was obvious the man did not have an explosive device.

The case comes as about 2,000 asylum-seekers remain on Christmas Island, where tensions are reportedly mounting among detainees.

Ms Sarah Hanson-Young, a Greens Senator in the national Parliament, said asylum-seekers were becoming frustrated at the length of time they were in detention.

"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 told the ABC.

Mr Ian Rintoul from the Refugee Action Coalition said he was aware of one man on Christmas Island who had stitched his lips together after being separated from his brother and his brother's family.

Such hunger strikes are intermittent among detainees sent to remote Pacific islands by Australia, notably in 2004, when a number of detainees in the tiny state of Nauru also sewed up their lips in protest at their status.

Mr Rintoul said on Tuesday that frustrations were growing among detainees who he said have been told they have no chance of resettlement in Australia, and will be sent to camps on Papua New Guinea's Manus Island or Nauru.

Under Australia's policies to stop asylum-seekers arriving in the country by sea, Canberra is refusing to accept any would-be refugees who arrive on people-smuggling boats, sending them instead to the Pacific camps.

Deputy Prime Minister Warren Truss said despite the criticisms, there was "widespread satisfaction" with the government's efforts to crack down on the people-smugglers bringing asylum-seekers to Australia by boat.

"I think that some of those who are critical of the government's approach to asylum-seekers don't want our policy to succeed," he told the ABC.

"They actually want open doors, they are not in favour of measures to protect our borders."