Seoul, August 31: A report by the UN nuclear watchdog suggesting that North Korea has restarted nuclear operations adds to the urgency of resuming talks with it, an official in the South Korean administration said on Tuesday.

The International Atomic Energy Agency said last week that a 5-megawatt nuclear reactor in Yongbyon appeared to be operational for the first time since December 2018. It said that a nearby radiochemical laboratory, which reprocesses spent nuclear fuel, was active for five months leading up to July.

"North Korea continuing to build up its nuclear arsenal means we should urgently engage the North to solve this problem," the official told reporters on condition of anonymity.

Lee Jong Joo, a spokesperson for South Korea's Unification Ministry, said on Monday that the South's government could not corroborate the UN agency's findings. He said South Korea was monitoring the North's nuclear activities together with the US and would continue making efforts to improve inter-Korean relations and achieve full denuclearisation of the peninsula.