The International Organization for Migration says more than 8,000 people have been displaced since violence erupted in Wau town three days ago.
In a statement, IOM says its tracking and monitoring teams were deployed to different sites in Wau over the past two days to assess the scale of new displacement.
The IOM says clashes were intense in areas south and west of Wau town, including near the Nazareth church displacement site.
It says the teams observed that many IDPs, who were camping at the Nazareth church compound, have left for the UN camp and the cathedral, in search for more secures areas.
The IOM says 4,000 people arrived at the UN base, joining more than 25,000 who are already sheltering at the site.
It says an additional 3,800 people arrived at the Cathedral site, which has been hosting nearly 8,000 people since June.
IOM says its teams and relief agencies are providing assistance to new arrivals at existing displacement sites.
The Chief of Mission, William Barriga, says humanitarian needs in Wau continue to grow because people fear to return to their homes.
He says the displacement figure is likely to increase over the coming days as families continue to seek protection at displacement sites.