UNITED NATIONS (Reuters) - The United Nations on Friday accused Khartoum of bombing a refugee camp in South Sudan and called for an investigation into an attack. "Yesterday UNMISS (the UN mission in South Sudan) confirmed that the Sudan Armed Forces dropped at least two bombs near the Yida refugee camp ... with unknown casualties," UN peacekeeping chief Herve Ladsous told a meeting of the UN Security Council. Khartoum has denied the allegations.Separately, UN human rights chief Navi Pillay in Geneva called for an investigation into the bombing, saying the information available so far suggested that the attack may be an international crime or serious human rights violation. "There needs to be an independent, thorough and credible investigation to establish the precise circumstances of this aerial bombing," Pillay said. "If indeed it is established that an international crime or serious human rights violation has been committed, then those responsible should be brought to justice," she said. UNMISS Chief Hilde Johnson told the council via video link that two bombs fell inside the Yida camp and three outside it. Ladsous said that UNMISS has relocated at least 12 aid agency and UN staff from the area and additional relocations are ongoing.