Thousands of children are likely to have been separated from their families as a result of the latest violence in South Sudan, an aid agency has warned.
Save the Children says many children are surviving on their own in very remote areas.
Some have witnessed their parents being killed and their homes looted or destroyed.
The fighting broke out two weeks ago in the capital Juba, and has spread to many parts of the country.
At least 1,000 people have died.
End Quote Helen Mould Save the ChildrenIn about three days alone we have registered 60 children in one site in Juba who have been separated from their families"
The positions of the warring factions in South Sudan seem to be hardening ahead of a regional deadline for talks to begin.
South Sudan only became independent from Sudan in 2011, after decades of conflict.
'Hiding in swamps'More than 121,000 people fled their homes when fighting started, with the result that many families were split up, Save the Children said.
The charity said while many people had sought refuge in UN compounds or host communities in safer areas, others, including children, were hiding in swampy areas with no shelter where they would be forced to drink stagnant water.
"In about three days alone we have registered 60 children in one site in Juba who have been separated from their families because of the conflict," Save the Children's Helen Mould told the BBC's Newsday programme.
"Until we get access to these areas where the fighting has been at its hardest, in Jonglei, in Upper Nile state… it's difficult to know what the exact circumstances are and it's difficult for us to respond," she said.
What began as a power struggle between rebel leader Riek Machar and President Salva Kiir has taken on overtones of an ethnic conflict. The Dinka, to which Mr Kiir belongs, are pitted against the Nuer, from which Mr Machar hails.
The government has offered a ceasefire, but the army says its forces are still battling rebels over oilfields in the north.
'No prisoner releases'East African mediators have given both sides until Tuesday to agree an end to hostilities.
But as the deadline looms, positions seem to be hardening, the BBC's James Copnall reports from Juba.
It had seemed as if the government was prepared to release several detained politicians - Mr Machar's main condition for beginning talks, he says.
However, senior government figures now say this will not happen, citing Mr Machar's refusal to accept the cessation of hostilities.
Please turn on JavaScript. Media requires JavaScript to play.
The BBC's James Copnall says aid workers fear a humanitarian crisis
Mr Machar says it is impossible to stop fighting before the talks, as verification mechanisms would need to be agreed on first.
Meanwhile, there are conflicting reports about a march by youths loyal to Mr Machar on the strategic town of Bor.
Claims that most of the fighters had gone home were later denied, and some of the youths are said to have clashed with government forces.
Mr Machar was vice-president until Mr Kiir sacked him in July.
Earlier this month fighting broke out between rival army factions after Mr Kiir accused Mr Machar of trying to unseat him in a coup.
