Khartoum - The medical needs of 165 000 Sudanese children are being held "hostage" by the warring parties in South Kordofan and Blue Nile states, a senior United Nations official said on Thursday.
Those children "are not accessing basic health services, including vaccination against measles and polio", Martin Mogwanja, deputy executive director for operations at the UN children's fund (Unicef), told reporters after a four-day visit to Sudan.
The youngsters are in rebel-held parts of the two states, where the Sudan People's Liberation Movement-North began an uprising in 2011 fuelled by complaints of political and economic neglect.
"It is not right for the different forces in conflict in those areas to hold these children as hostage, to hold their future as a hostage for the completion of a political process," Mogwanja said.
His appeal is the latest by the UN, which had brokered a November ceasefire between the two sides in order to carry out a polio vaccination campaign in the rebel-held zones as part of a nationwide effort.
But the warring parties would still not let aid workers in, and UN humanitarian operations director John Ging earlier blamed a "filibuster" by both the government and rebels.
If the campaign were to go ahead, it would be the first aid access into SPLM-N areas from within Sudan since 2011.
A broader internationally-backed plan to get food and other assistance to the rebel zone fell through more than a year ago despite months of talks with rebels and the government.
"We cannot afford to forget these children," Mogwanja said. "This must be a priority for everyone."
In April, the first peace talks in almost two years between the rebels and government stalled over the issue of humanitarian access.
The UN Security Council has stressed the need for a political solution to the conflict.
Sudanese authorities have severely restricted access to the warzones for aid workers, journalists and foreign diplomats.
Mogwanja said that in many cases Unicef is not able to be present in Sudan's conflict areas, and he did not know how many children have been killed because of the war in South Kordofan and Blue Nile.
But he said: "Children are not actors in any of these conflicts. They should not be targets and they should not be victims."
More than one million people have been severely affected or displaced by the fighting in South Kordofan and Blue Nile, the UN says.
Mogwanja did not visit the two states but travelled to the Darfur region, where over one million people live in camps for those displaced by a decade of fighting between government and rebels, as well as a recent upsurge of inter-Arab violence.
He visited North Darfur's Zam Zam camp, where some children "may have been exposed to active conflict... to shooting, killing, bombing," which he said could cause long-term trauma to children.
Mogwanja said the conflict, which is occurring in half of the country's 19 states, is helping to "undercut the opportunities for the children of Sudan to survive and thrive."
He said at least 4.1 million children are in need of urgent humanitarian assistance, more than 1.8 million are out of school, and an estimated 750,000 need treatment for severe acute malnutrition.
"This is an extremely concerning figure," Mogwanja said.