A U.S. daily says North Korea has become increasingly belligerent since its leader Kim Jong-il recovered from a stroke-like illness last October.

The Wall Street Journal quoted observers as saying Tuesday that Pyongyang’s detention and imprisonment of two U.S. journalists and a South Korean worker is adding to a pattern of increasingly belligerent behavior that started when Kim’s health improved.

The report cited that the North launched a rocket in early April and is now threatening to conduct another nuclear test.

The daily said hard-line figures tied to the North's military have gained power since Kim's illness and are forcing an end to the diplomatic processes that raised barriers to the country's development of nuclear weapons.