Four Protestant paramilitary prisoners have gone on hunger strike in protest at conditions at Northern Ireland's largest jail, officials said on Tuesday.
The move marks an escalation in a battle of wills between prison authorities and "loyalist" guerrilla inmates following a riot at Maghaberry Prison, 20 miles (30 km) southwest of Belfast, last week.
"Four prisoners have declared themselves to be on hunger strike and have been refusing prison food, two since Sunday, one from Monday and one from today," said a spokeswoman for the Northern Ireland Prison Service.
"It's not officially noted as a hunger strike until they have refused food for 24 hours.
Prisoners' representatives outside the jail said they were refusing food to protest against conditions at Maghaberry and to demand complete segregation from Catholic republican prisoners.
"What's happening is there's one (prisoner) going on hunger strike every day," said Frankie Gallagher, a spokesman for the Ulster Political Research Group, which speaks on behalf of the largest loyalist group, the Ulster Defence Association.
"We have arranged to meet the prison authorities on Wednesday to try and create a window of opportunity for some serious dialogue.
In 1981, 10 republicans demanding to be treated as political prisoners died on hunger strike in the now closed Maze Prison, but there is little history of loyalist hunger strikes.
The dispute at Maghaberry has been simmering for months. A week ago 35 loyalist prisoners rioted inside the jail, lighting fires and barricading themselves on their wing.
After violent clashes in September, Britain bowed to demands to separate loyalists from republicans, and new prison blocks are being prepared to house the opposing factions.
But the authorities say they are determined not to bow to pressure from inmates for a return to the type of regime operated in the notorious "H-Blocks" of the Maze, where prisoners effectively ran their own parts of the jail.
The Maze was closed in 2000 with the release of most guerrilla prisoners in the wake of the 1998 Good Friday peace agreement, which aimed to end three decades of violence.
Paramilitary prisoners at Maghaberry have been convicted of offences since the 1998 accord or are members of groups which did not declare ceasefires in tandem with the peace deal.