Japan has extended the measures three times since the nuclear test
Japan has again extended the economic sanctions it imposed on North Korea after its nuclear test in October 2006.
Officials put the move down to a lack of progress on denuclearisation and a row over Japanese nationals abducted by Pyongyang in the 1970s and 1980s.
The measures - which ban imports from North Korea and visits by its ships - will continue for another six months.
The move comes with progress on a deal aimed at ending Pyongyang's nuclear programme, stalled since late 2007.
Earlier this week, US and North Korean negotiators said they had narrowed their differences over the key issue holding up the talks.
The US wants Pyongyang to provide a complete declaration of all of its nuclear activities - including an alleged secret uranium enrichment programme.
'No concrete steps
Japan imposed the sanctions days after Pyongyang conducted its first nuclear test on 9 October 2006.
Chief Cabinet Secretary Nobutaka Machimura said the decision to extend again related to the deadlocked talks.
"North Korea hasn't made a complete and correct declaration on its nuclear programmes yet," he said.
"Taking into account of situations surrounding North Korea, we have decided that we need to keep the sanctions."
Pyongyang had also "not taken any concrete steps regarding the kidnapping issue", he said.
North Korea admitted in 2002 that it had kidnapped 13 Japanese nationals to train spies.
It has returned five of them and says the remaining eight are dead. It says the issue has now been resolved.
But Japan wants concrete proof of the deaths and believes that several more of its citizens were taken.
There is huge public concern over the issue in Japan, but talks between the two sides have made no progress in recent months.