South Sudan has accused the government of neighbouring Sudan of arming gunmen alleged to have killed dozens of people in a cattle raid, as the UN warned that tensions between the two sides risked regional peace. 'A militia group from Unity state penetrated into Warrap state... and attacked people in a cattle camp, killing over 40,' Alison Manani Magaya, South Sudan's interior minister, said on Monday following the latest violence in the world's newest nation, which ceded from Sudan last year.