Japan said on Tuesday it would respond "harshly" if the Democratic People's Republic of Korea (DPRK) conducted a nuclear test.

"Japan and the world would definitely not tolerate a nuclear test (by the DPRK)," Prime Minister Shinzo Abe was quoted as saying by Kyodo News.

"If the test is carried out, I believe the international community would respond harshly," he said.

The DPRK's Foreign Ministry announced on Tuesday that it would conduct a nuclear test in the future as a war deterrent against the hostile U.S. policy.

"It's clear that this kind of action will naturally have a significant impact on Japan and the whole of Northeast Asia... (and) pose a threat to peace," Japanese Foreign Minister Taro Aso told reporters.

"It's simply unforgivable," he said.

In a statement issued by its Foreign Ministry, the DPRK said "(for) scientific research, the DPRK will in the future conduct a nuclear test under conditions where safety is firmly guaranteed," according to the official Korean Central News Agency (KCNA).

The statement did not give specific date or location for the upcoming test.