The United Nations refugee agency (UNHCR) on Friday called on governments to allow civilians fleeing Sudan into their territory and not to send them back to the conflict-torn country.

"We're advising governments not to return people to Sudan because of the conflict that's going on there," Elizabeth Tan, UNHCR's Director of International Protection, told reporters at a briefing in Geneva.

"This applies to Sudanese nationals, to foreign nationals, including refugees who are being hosted in Sudan, stateless persons, as well as those who do not have a passport or any other form of identification," Tan said.

The conflict in Sudan has forced about 100 000 people to flee to neighbouring countries, according to the UN, and has hindered aid deliveries in a country where about one-third of people already relied on humanitarian assistance.

Tan said there was no indication that civilians from Sudan were not being allowed to enter neighbouring countries, even though there was a build-up of people at the border with Egypt.

"There are likely to be high levels of international protection needs amongst those who are fleeing," Tan said of civilians fleeing Sudan.