North Korea appears to be renovating and building facilities at its Yongbyon nuclear site, a central element of its atomic weapons program, the U.N. nuclear agency's head said on Monday.
A report by the Washington-based Institute for Science and International Security (ISIS) in April said satellite images showed that activity at the site's main nuclear reactor may have resumed after a shutdown.
North Korea, which is believed to have carried out nuclear tests in 2006, 2009 and 2013, has not granted IAEA inspectors access to its facilites since 2009, reducing the agency to monitoring its nuclear activities from outside the country.