North Korea is reportedly about to carry out a nuclear test imminently to coincide with national celebrations. Monitoring group 38 North said that satellite images showed that the secretive state was "primed and ready" for a sixth nuclear test as early as Saturday (15 April).
The website of 38 North said that imagery of the country's Punggye-ri nuclear test site showed activity around its north portal. There was also new activity in the main administrative area and personnel have been seen around the site's command centre, it added.
"In the courtyards of the main administrative area are approximately 11 probable tarp-covered pallets of equipment or supplies, a formation of personnel, and several individuals walking about," the site said.
38 North analyst Joseph Bermudez told CNN: "The activity during the past six weeks is suggestive of the final preparations for a test."
International journalists in the country for the 105th birth anniversary of the state's founder Kim Il-sung were told by the government to get ready for a "big and important event" amid speculation that the regime wanted to coincide a missile launch with the celebrations on Saturday (15 April).
Reporters, including ones from Japan and the US were taken to opening of a high-rise residential complex in Pyongyang which leader Kim Jong-un attended, the Guardian reported.
However South Korean officials tried to allay concerns that there was to be a nuclear test, with a spokesman for the country's joint chiefs of staff saying there had been "no unusual activity so far".
Tensions have been ratcheted up after the deployment of the USS Carl Vinson and its strike group said to be about to undertake drills with Japanese vessels near the Korean peninsula.
Following talks with Donald Trump, the Chinese president Xi Jinping said that Beijing was committed to de-escalating the tensions "through peaceful means".
"China remains committed to the goal of denuclearising the (Korean) peninsula, safeguarding peace and stability on the peninsula, and advocates resolving problems through peaceful means," the Chinese state broadcaster CCTV quoted Xi as saying.
But state newspaper Global Times reported that the US airstrike on Syria raised the prospect that Washington would respond to Pyongyang provocation even without Beijing's support, saying: "The Korean peninsula has never been so close to a military clash since the North conducted its first nuclear test in 2006".
Japanese Prime Minister Shinzo Abe said on Thursday that North Korea might be able to fire missiles equipped with sarin nerve gas.