North Korea has built a new uranium enrichment facility at its main Yongbyon nuclear complex that could house up to 28 centrifuge cascades, and started operating an expanded annex at its Kangson enrichment site, the International Atomic Energy Agency (IAEA) said. The Vienna-based nuclear watchdog said in a report the findings pointed to a steady expansion of North Korea's nuclear infrastructure at multiple locations. In the report, dated August 28, the IAEA said it relied on satellite imagery and open-source material, including photographs published by North Korean state media, to track Pyongyang's nuclear activities. The agency has had no inspectors in North Korea since 2009. It identified a new two-storey building at Yongbyon as the site's second uranium enrichment facility by comparing state media photographs of a June visit by North Korean leader Kim Jong-un with satellite images taken during the building's construction. Photographs from the visit indicate gas centrifuge cascades are installed on both the upper and lower floors of the main building, the report said, adding the buildi