Pyongyang has slammed Tokyo for declaring that the remains the North handed over last month are not those of Japanese abductee Megumi Yokota, the Korean Central News Agency said.

A North Korean Foreign Ministry spokesman said in a statement that Pyongyang has concluded that Japan's DNA tests on the ashes were based on a political plot meticulously prearranged to achieve a certain objective, the official North Korean news agency said Tuesday.

The statement added that Pyongyang would take any imposition of retaliatory economic sanctions by Japan as "a declaration of war" and swiftly retaliate with "strong physical deterrents."