[SEOUL] Analysis of recent satellite images suggests North Korea may be moving forward with preparations to conduct a fifth nuclear test in the near future, a US think-tank said Saturday.
The pictures, dated May 5, show closely parked vehicles at what is believed to be the test command centre, some six kilometres (four miles) south of the underground detonation site at Punggye-ri in the country's northeast.
"While the historical record is incomplete, it appears that vehicles are not often seen there except during preparations for a test," said the analysis by the US-Korea Institute at Johns Hopkins University.
Although the actual test site continues to show "low levels" of activity, the vehicle presence "suggests Pyongyang may be preparing for a nuclear test in the near future," it said.
On Friday, North Korea kicked off a rare and much-hyped ruling party congress that numerous analysts had predicted could be preceded by a fresh nuclear test.
South Korean officials have not ruled out the possibility of a test being conducted during the party conclave, which is expected to last three or four days.
North Korea has conducted four nuclear tests. The most recent was on January 6, with Pyongyang claiming it marked the country's first successful test of a powerful hydrogen bomb.
The UN Security Council responded by imposing its strongest sanctions to date over the North's nuclear weapons programme.
In his opening speech to the party congress on Friday, North Korean leader Kim Jong-Un hailed the "magnificent" strides the country had made with its nuclear weapons programme in the face of "malicious pressure and sanctions."