The 255 Sri Lankan asylum seekers aboard a boat in western Java have unfurled a large banner declaring a hunger strike.

The ethnic Tamils are refusing to leave their wooden boat in Merak Harbour, after being intercepted at sea at the weekend on their way to Australia.

Speaking from the boat via mobile phone, the spokesman who calls himself 'Alex' says that the hunger strike excludes anyone aged under 21.

"The only reason we came to the conclusion of a hunger strike is any other demonstration of violence will only give a bad image on us, and we want the world to know that we're not bad people, we are good people," he said.

"We will hunger strike until death, we will hand our children over to die and we will hunger strike until death."

The hunger strike was called after Indonesian authorities began surveying local options to accommodate the asylum seekers in hotels and guest houses, because detention centres are too full.

'Alex' was led away to inspect the accomodation but others on the boat were apparently worried that his actions may send the wrong signal.

'Alex' then returned to the boat, and after a debate he helped unfurl the hunger strike banner.

"We have got some information to say that the navy is about to try to get us off the boat because no country is about to take us and they want to try to get us to land," he said.

"So we decided on the strike to let the whole world know that we need their assistance as soon as possible. We need somebody to consider our case."

The words life and death are written in the banner's corner alongside a question mark.

The group wants to be immediately accepted as refugees into a third country and does not want to enter the United Nations system, in which claims can take up to 10 years to process.

The asylum seekers' boat was intercepted by Indonesian authorities after Prime Minister Kevin Rudd personally spoke to President Susilo Bambang Yudhoyono.

Australia says responsibility for the group of asylum seekers now rests with Indonesian immigration officials.

Banten Province's immigration chief, Dr Harry Purwanto, has rejected suggestions the Sri Lankans will be moved to Indonesian detention centres.

He says the centres are too full and authorities are instead scouting local hotels and guest houses as possible places to house the asylum seekers.

Indonesian officials say the Sri Lankans will not be forced to come ashore and there is no time limit on their decision.

However, immigration officials suggest negotiations may take one to three days; the navy says not more than a week.

Limited places

But the United Nations says it is possible the group of asylum seekers will end up in Australia.

The regional spokesman for the UN's Refugee Agency, Richard Towle, says his staff in Indonesia will deal with anyone who wants to claim asylum.

But he says there could be delays because the number of places available for refugee resettlement are limited.

"They could end up in Australia and that again is not a new phenomenon. Australia takes recognised refugees from Indonesia on a regular basis and has a generous tradition of doing that," he said.

"The number of available places internationally to resettle refugees is quite limited.

"The key states that offer resettlement places globally have only limited capacity to take refugees and that's where we often get the delays. It's not in the UNHCR processing side, it's in finding states that are willing to accept cases on a resettlement basis."

The asylum seekers are clearly desperate. On Wednesday night members of the group made a direct plea to Mr Rudd for help, telling reporters they were fleeing "genocide" in Sri Lanka and feared being killed if they were returned to the country.

It is possible they are talking to people via mobile phones and gathering information about some of the media reaction from Australia.

The asylum seekers keep repeating to the media that they are not terrorists.

In stark contrast to their threat to blow themselves up on the boat earlier this week, they are now trying to deliver a softer line, saying that they want international assistance.