North Korea has virtually finished preparations for nuclear tests in two tunnels at the Punggye-ri nuclear test site in North Hamgyong Province, observers believe.
A South Korean government source said analysis of satellite images showed brisk activity of support vehicles and personnel at a tunnel on the southern side of the test site, and on Saturday the area was cleaned and personnel left.
Intelligence agencies suspect that this means a nuclear test is imminent. Preparations at a tunnel on the western side of the site were apparently completed earlier.
The government here is now watching for the possibility of two separate nuclear tests either simultaneously or in quick succession.
"There is a chance that the southern tunnel is a decoy, but we aren't ruling out that the regime will conduct nuclear tests simultaneously at both tunnels," a military source said.
The source said it might help North Korea to produce smaller nuclear warheads that could be mounted on missiles if it tests a couple of different devices at the same time.
In 1998, Pakistan conducted eight nuclear tests over two days, which allowed it to accelerate the miniaturization of nuclear weapons.