There are fears North Korea is likely to conduct its fifth nuclear test in the coming weeks.

Based on readings of the activity around the country’s nuclear test, South Korean officials estimate the test could come before its party congress in early May.

Pyongyang is currently gearing up for a ruling Workers Party congress in early May, where leader Kim Jong Un is likely to boast about his achievements in building a weapons programme.

The likelihood of North Korea conducting a fifth nuclear test, possibly within weeks, has increased because of a failed missile launch on Friday.

The failure was an embarrassing setback for leader Kim, South Korean officials and international experts said.

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Several government sources said: "Compared to last month, the frequency of vehicle, workforce and equipment movements increased two-to-threefold recently."

The possible test, if it happens, follows a fourth nuclear test in January and a long-range rocket launch in February, which led to new U.N. sanctions that have failed to halt Pyongyang's weapons programmes.

South Korea's military has said Pyongyang is technically ready for an additional nuclear test, depending on its leadership's political decision.