Japan will shoot down any ballistic missiles launched by North Korea it considers to be a threat, a government source said.
A Japanese destroyer has been dispatched to the Sea of Japan with orders to fire if North Korea launches any missiles that Tokyo deems in danger of hitting Japanese territory in the next few weeks, the source said.
The order, issued by Japanese defence minister Itsunori Onodera, was not made public to avoid jeopardising renewed talks between Tokyo and Pyongyang, local media reported.
Tensions have been ratcheting up in the region since Pyongyang test-fired two of its Rodong medium-range missiles over the sea just as Japan, South Korea and the US were sitting down to talks aimed at resolving tensions in the region.
Both missiles stopped halfway in their maximum range plummeting into the sea.
And last week South Korean military forces returned fire after North Korean artillery shells fall in their territory in the disputed Yellow Sea border region during military exercises.
Pyongyang has defended its recent short-range launches, saying that the drills are in preparation for an attack, and a test of its own weapons systems.
North Korea's foreign ministry has condemned UN Security Council criticism of the drills.The ministry added that Pyongyang would "categorically" reject any subsequent UN sanctions as a breach of sovereignty.
According to a North Korean government source: "[The firing drills are] justifiable self-defence behaviour for us to conduct to preserve peace in the region and to protect the safety of our people and our country."
Pyongyang has also declared a no-sail zone off its east coast following the missile drills.