VIENNA (AFP) - Iran has started enriching uranium at higher levels, according to a new restricted UN atomic watchdog report obtained by AFP. Iran provided the (International Atomic Energy) Agency with mass spectrometry results which indicate that enrichment levels of up to 19.8 percent (uranium) were obtained, the report said. The enrichment was carried out at a plant in Natanz between February 9 and 11, said the IAEAs director general Yukiya Amano in his first report to the board of governors. Iran started feeding the nuclear material into the uranium-enriching centrifuges before IAEA inspectors had arrived at the plant, the report added. On February 10, when the agency inspectors arrived at PFEP (Pilot Fuel Enrichment Plant), they were informed that Iran had already begun to feed the UF6 (uranium hexafl-uoride) into one cascade the previous evening, it said. According to the report, the UN atomic watchdog is concerned that its information about Irans nuclear activities suggests the Islamic republic may be working on a nuclear warhead. The information available to the agency ... raises concerns about the possible existence in Iran of past or current undisclosed activities related to the development of a nuclear payload for a missile, the watchdogs chief Yukiya Amano wrote in his first report to its board of governors. It was the first time the Vienna-based International Atomic Energy Agency (IAEA) had expressed such concern about current activities, as it has only referred to past activities in previous reports. Iran started feeding the nuclear material into the uranium-enriching centrifuges before IAEA inspectors had arrived at the plant, the report added. UN inspectors had verified that none of Irans declared nuclear material had been diverted, the report said. However, Iran has not provided the necessary cooperation to permit the agency to confirm that all nuclear material in Iran is in peaceful activities.