The UN atomic agency has \"serious concerns\" about Iran\'s nuclear activites, and has \"credible\" information Tehran may have worked on developing atomic weapons, a report seen by AFP said Tuesday. \"The agency has serious concerns regarding possible military dimensions to Iran\'s nuclear programme,\" the keenly awaited International Atomic Energy Agency report said, saying its information is \"overall, credible.\" \"This information indicates that Iran has carried out activities relevant to the development of a nuclear explosive device,\" calling on Tehran to \"engage substantively with the agency without delay.\"