UN nuclear watchdog ‘monitoring’ new construction in North Korea

"The agency is monitoring the construction of a new building at Yongbyon, which has dimensions and features similar to the Kangson enrichment plant," IAEA Director General Rafael Grossi said at a news conference.

Grossi also expressed "serious concern" over the "undeclared" enrichment facilities at Kangson and Yongbyon.

"The continuation and further development of the ... nuclear program are clear violations of relevant UN Security Council resolutions and are deeply regrettable,” he said.

Grossi added that he hopes to engage in a "constructive and mutually beneficial" way with North Korea, saying the agency stands ready to verify the nuclear program.

North Korea has been under sweeping UN arms embargoes since 2006 due to its nuclear program, with sanctions repeatedly tightened to restrict nearly all arms imports and exports.

A UN committee was set up in 2006 to monitor sanctions enforcement, but its mandate expired last year after Russia vetoed its extension.

Last September, North Korea publicly disclosed a uranium enrichment facility for the first time, as leader Kim Jong Un called for expanding the country’s nuclear capabilities.

In 2010, North Korea allowed US nuclear expert Siegfried Hecker to tour its uranium enrichment facility in Yongbyon, around 100 kilometers (62 miles) north of Pyongyang.

The site is home to the Yongbyon Nuclear Science and Weapons Research Center, which operates the country’s first nuclear reactors.