Juba - The United Nations says some people fleeing South Sudan into Uganda are forced to pay bribes at checkpoints run by South Sudan's government and armed groups.It also says it has received reports of physical and sexual assaults and forced family separations.More than 100 000 South Sudanese have fled to Uganda after deadly fighting rocked the capital, Juba, in July.A spokesman for the U.N. refugee agency, Rocco Nuri, calls the reports of refugees being forced to pay bribes to reach safety "disturbing."The United Nations last week announced that over one million South Sudanese have fled the country since a civil war began in December 2013. A peace deal signed in August 2015 has not stopped the fighting.Uganda has taken in the highest number of refugees.South Sudan's southern region bordering Uganda is centered on the town of Yei."You will find people detained and you don't know why, you will find a family slaughtered and you don't know why," a civilian living in Yei told The Associated Press in a recent interview.The civilian, who spoke on condition of anonymity for fear of retribution from the government, said civilians pay around $200 to leave for Uganda and are forced to pay bribes at government checkpoints along the way.Stephen Ladu, Yei River State's information minister, referred accusations of arbitrary arrests to the governor, who was not immediately available for comment. "There are a lot of ambushes and unknown gunmen on the road," Ladu said.