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 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 facilities since 2009, reducing the agency to monitoring its nuclear activities from outside the country.
"We have observed renovation and construction activities at various locations within the site," IAEA Director General Yukiya Amano told a closed-door meeting of his agency's Board of Governors in Vienna, according to a text of his speech.
"These appear to be broadly consistent with the DPRK's statements that it is further developing its nuclear capabilities," he said, referring to North Korea's official name, the Democratic People's Republic of Korea.
Although North and South Korea recently averted a full-scale military confrontation, and agreed to improve ties after a rare exchange of artillery fire over their heavily fortified border, tensions on the Korean Peninsula remain high.
China, North Korea's closest ally, called on Wednesday for a resumption of talks over Pyongyang's nuclear program.
The so-called six-party talks — between China, the United States, Japan, Russia and the two Koreas — were last held more than six years ago despite numerous efforts to restart them.
The ISIS report in April said the main reactor at Yongbyon may be operating again at low power or intermittently, and that a centrifuge plant, a facility for the enrichment of uranium, had operated. It also said renovations might be imminent.
Amano did not say where within the Yongbyon site the renovation and construction activities were being carried out.
"We continue to monitor developments at the Yongbyon site, mainly through satellite imagery," said Amano.