The top UN humanitarian official on Wednesday appealed for access to all those in need in the strife-torn region of South Sudan, where humanitarian situation has deteriorated due to the clashes.

"I am alarmed by the deteriorating humanitarian situation in Pibor County in Jonglei," where some 100,000 civilians have been cut off from life-saving aid due to clashes, the Under-Secretary- General for Humanitarian Affairs, Valerie Amos, said in a statement issued here by her office.

Fighting between state and non-state armed actors, and the recent resurgence of inter-communal clashes are threatening the lives of ordinary people and have reduced the ability of humanitarian organizations to provide urgently needed help, according to the statement.

"I call on all parties to stop the violence immediately, to prevent further unnecessary loss of life, and to create the necessary security environment conducive for aid delivery," she said.

Amos, who also serves as the Emergency Relief Coordinator, emphasized that "as long as the fighting continues, delivery of aid will be limited and we will not get help to those who need it. "

In addition, she underscored that the UN will work with all parties to ensure people in need receive humanitarian assistance and remind all sides to respect their obligations under international humanitarian law to protect civilians.

Jonglei, the largest state in the eastern part of South Sudan, has been the scene of inter-communal violence since the country won its independence on July 11, 2011 from Sudan under a peace deal.