More than 250 asylum seekers are on a hunger strike on Manus Island over their frustration at being held in detention for the past 17 months without being given any guarantee about their futures, refugee advocates say.

The asylum seekers, believed to be men from Pakistan, Syria, Iran and Iraq, have been protesting since Wednesday.

Housing on Manus Island.

Advocates said two of the men had sewn their lips shut in frustration over only 130 of 1200 detainees having been processed.

Refugee Action Collective spokesman Chris Breen said those who had been processed had been offered a one-year temporary visa, which they will need to reapply for annually.