North Korea is showing a "very serious increase" in its ability to produce nuclear weapons, the head of the International Atomic Energy Agency (IAEA) has said.
South Korea's spy agency has said it is believed that North Korea operates multiple facilities for enriching uranium, a key step in making nuclear warheads,
They include one at the Yongbyon nuclear site, which Pyongyang purportedly decommissioned after talks but later reactivated in 2021.
"In our periodic assessments, we have been able to confirm that there's a rapid increase in the operations" of the Yongbyon reactor, IAEA chief Rafael Grossi said at a news conference in Seoul.
The agency had also observed a rise in operations at Yongbyon's reprocessing unit and light-water reactor, as well as the activation of other facilities, Mr Grossi said.
"All that points to a very serious increase in the capabilities of (the) DPRK in the area of nuclear weapons production, which is estimated at a few dozen warheads," he said, referring to North Korea by its official name.
North Korea, which conducted its first nuclear test in 2006, is under rafts of UN sanctions for its banned weapons programmes.
It has declared that it will never surrender its nuclear weapons.
Asked whether Russia was assisting North Korea's nuclear development, Mr Grossi said the IAEA had not seen "anything in particular in that regard".
North Korea has sent ground troops and artillery shells to support Russia's invasion of Ukraine, and observers say Pyongyang is receiving military technology assistance from Moscow in return.
Yesterday, North Korean leader Kim Jong-un oversaw new tests of strategic cruise missiles and anti-warship missiles launched from a naval destroyer, state media reported.
The weapons tests occurred on Sunday, the state-run Korean Central News Agency (KCNA) said, and are the latest in a string of recent missile launches.
Two strategic cruise missiles each flew for just over two hours, according to KCNA, while the anti-warship missiles flew for 33 minutes.
The missiles flew "along the flight orbits set in the sky above the West Sea of Korea and struck the targets with ultra-precision hit accuracy", KCNA said, using its preferred name for the Yellow Sea.
The tests were carried out from the Choe Hyon, one of two 5,000-ton destroyers in the North's arsenal, both launched last year as Mr Kim seeks to ramp up the country's naval capabilities.
A photo released by KCNA showed a missile in its initial flight stage after being launched from the warship, with an orange flame trailing from its tail.
KCNA said Mr Kim was also briefed on planning for the weapons systems of two more destroyers under construction, referred to simply as "Nos. 3 and 4".
He reportedly "expressed great satisfaction over the fact that the preparedness of our army's strategic action has been strengthened".
He reiterated that bolstering the North's nuclear deterrent was the "most important priority task".
