N.Korean moves indicate imminent nuclear test: sources

A series of activities detected at North Korea's nuclear test site indicate the communist state is on the verge of another nuclear bomb test, according to South Korean officials.

The government officials said an analysis of intelligence and satellite photos on the North's Punggye-ri nuclear test site shows a sharp increase in vehicle and human activities there in recent weeks.

The North Korean moves have prompted South Korean authorities to conclude that Pyongyang is likely to conduct its fifth nuclear test before early May, they added.

There have been growing concerns about potential military provocations by Pyongyang, including additional nuclear and ballistic missile tests, before its scheduled first congress of the ruling Workers' Party of Korea in more than three decades in early May.

South Korea is now closely monitoring the nuclear site to look for any signs of a miniaturized nuclear warhead being used in the new test.

North Korea has claimed to have secured key technologies to fire an intercontinental ballistic missile and threatened to conduct a detonation test, with a nuclear warhead loaded onto an ICBM.