The detainees, held in seven detention centres across the United Kingdom, refused breakfast yesterday and say that they will refuse all further meals until Saturday morning.
They say they are also demonstrating against conditions in the centres. Their complaints include allegations of verbal and physical abuse by staff.
The detention centres involved in the protest are Harmondsworth, Tynsley House, Haslar, Lindholme, Colnbrook, Dungarvel and Yarls Wood.
The exact number of protesters is not known, but speaking from Yarls Wood centre, a 24-year-old Zimbabwean woman told the Guardian that at least nine women in the female section of the centre were taking part in the protest.
A Home Office spokesman said: "We strongly dispute the figure of there being 200 people on hunger strike in the detention estate."
