JUBA : A top army commander in the troubled new nation of South Sudan has been arrested over a string of alleged human rights violations, officials said Tuesday. General James Otong Riek was a commander in the eastern state of Jonglei, the scene of heavy fighting last month between rival ethnic groups. The army said he had been implicated in "several reports and complaints of killings". Over 100,000 people were affected during the July fighting, when thousands of gunmen from the Lou Nuer tribe in northern Jonglei marched south towards Pibor, an area of their rivals, the Murle.