Four days after its nuclear test returned the region to a state of emergency, North Korean marked the anniversary of its departed 'Dear Leader' Kim Jong-il's birth on 16 February with a military parade, mass dances and televised sporting activities including synchronised swimming.

In Pyongyang, well-wishers bowed and laid floral wreaths at the foot of statues to the late leader and his son and successor Kim Jong-un, on what has been designated the 'Day of the Shining Star' in memory of the elder Kim, who died in December 2011.

Kim Jong-un visited his father's grave at the Kumsusan Palace of the Sun, according to the official Korean Central News Agency (KCNA). Other state-run media broadcast pictures of national ceremonies in honour of Kim, who would have been 71 today.

"Our soldiers and people celebrated the birth of our great leader after we showed our strength and braveness with the successful nuclear test," the KCNA said.

Athletes from several nations, including Russia, were due to attend sporting events in the capital.

In defiance of the international community, Pyongyang conducted its thrid nuclear test on 12 February, claiming its latest move was a riposte to UN sanctions imposed after the North's long-range rocket launch in December, which it claimed was part of a legitimate space programme.

This week's test drew international condemnation, with US President Barack Obama pledging to "lead the world in taking firm action in response to these threats".

South Korean Defence Minister Kim Kwan-jin said the tests showed the North's weapons had a range of about 6,200 miles, making the west coast of the United States a potential target.

In the South Korean bordertown of Imjingak, defectors from the North released hundreds of thousands of helium balloons containing anti-regime leaflets and $1 currency notes, and bearing slogans declaring "Stop provocative acts with missiles and nuclear tests", "North Koreans rise up" and "The Kim dynasty will soon collapse".

Pyongyang has in the past threatened a "merciless military strike" in response to anti-regime propaganda leaflets, forcing the evacuation of residents.

In separate developments, officials from the North have reportedly informed counterparts in China that further nuclear tests and rocket launches are planned for this year, with Pyongyang seeking to force the US into negotiations, a source told Reuters.

North Korea remains technically at war with both the United States and South Korea after the Korean war ended with a truce in 1953. Commentators interpreted the North's aggressive move as a statement by its new leader that he plans to follow his father's "military first" strategy.

Click below to see the synchronised swimming display to mark Kim Jong-il's birthday.