South Korean government says there are signs the regime is getting ready for what would be its fourth nuclear weapon test

This article is more than 7 years old

This article is more than 7 years old

North Korea could be preparing to conduct a fourth nuclear test, following signs of activity at the country's main testing site, South Korea's unification minister, Ryoo Kihl-jae, said on Monday.

Ryoo told a meeting with MPs at the national assembly that Seoul had acquired evidence of increased movement of vehicles and personnel at Punggye-ri, the Yonhap news agency said.

The site on North Korea's north-east coast is where the country's three previous controlled nuclear detonations – in 2006, 2009 and on 12 February this year – took place.

Ryoo's comments came after a South Korean newspaper quoted an unnamed government source as saying that workers appeared to be preparing for another test at Punggye-ri.

The JoongAng Ilbo quoted the source as saying that South Korean intelligence had detected "increased activity of labour forces and vehicles" at the site.

"We are closely monitoring the ongoing situation, which is very similar to the situation ahead of the third nuclear test. We are trying to figure out whether it is a genuine preparation for a nuclear test or just a ploy to heap more pressure on us and the US," it said.

The prospect of a nuclear test is certain to add to tensions on the peninsula amid reports that the regime in Pyongyang could be planning to launch a medium-range missile from its east coat, possibly as early as Wednesday.

Any missile launch is expected to be a test rather than a targeted strike and could take place in the runup to the 101st anniversary of the birth of North Korea's founder, Kim Il-sung, on 15 April. Another significant date is the anniversary of the foundation of the Korean people's army 10 days later.

Last week, North Korea warned foreign embassies in Pyongyang it could not guarantee their safety from the threat of conflict after Wednesday this week and advised them to consider pulling their staff out of the capital.

The North has unleashed a barrage of threats since the UN imposed sanctions in response to February's nuclear test. It has also been angered by military exercises involving South Korea and the US that are due to run to the end of the month.

The regime has threatened to launch nuclear strikes against the US mainland and its bases in the Pacific, declared itself in a "state of war" with South Korea and cut its military hotline with Seoul.

Last week, it banned South Korean workers from entering the Kaesong industrial complex – a jointly run enterprise located just north of the heavily armed border dividing the peninsula and an important source of hard currency for Pyongyang. The ban remained in place on Monday.

The North's latest moves are being seen as an attempt to push fears of an impending military crisis in the hope of winning concessions from Washington. There are no signs that the regime is mobilising its army of 1.2 million in preparation for any sort of attack.

The chairman of the US joint chiefs of staff, General Martin Dempsey, said he did not believe the North would take military action, but added: "I can't take the chance that it won't."

The US has brought forward the deployment of a missile defence system to Guam, a US territory in the Pacific. It has drawn up plans with South Korea on how to respond to specific military provocations by the North.

The allies would "respond more forcefully than in the recent past but in a limited way intended to prevent an escalation to broader war", the New York Times said, citing Pentagon officials.

A nuclear test would anger China, which has shown signs of growing frustration with North Korea, a major recipient of Chinese aid.

The Chinese president, Xi Jinping, alluded to North Korean provocations when he said no country "should be allowed to throw a region and even the whole world into chaos for selfish gain" in a speech on Sunday.

In a telephone conversation with the UN secretary general, Ban Ki-moon, at the weekend, China's foreign minister, Wang Yi, said Beijing "opposes provocative words and actions from any party in the region and do not allow trouble-making on China's doorstep", according to the ministry's website.

The commander of the 28,000 US troops based in South Korea, General James Thurman, abruptly cancelled a visit to Washington where he had been due to testify before congressional committees. Thurman would remain in Seoul as a "prudent measure", according to a US military official quoted by the Associated Press.

The chairman of South Korea's joint chiefs of staff, General Jung Seung-jo, also cancelled a visit to Washington later this week in light of rising tensions at home.

Dan Pfeiffer, an adviser to President Obama, said the administration "wouldn't be surprised" if the North conducted a missile test or similar provocation.

Pfeiffer told ABC's This Week that the North should "stop their actions, start meeting their international obligations and put themselves in a position where they can achieve what is their stated goal, which is economic development, which will only happen if they rejoin the international community".