Kawasaki Heavy Industries said on Thursday it aimed to make Japan's first ventilators to be used in underground shelters in 2026, as neighboring China intensifies a military buildup and North Korea boosts its nuclear and missile arsenal.

"First of all, these are for shelters for disaster response in natural disaster-prone Japan. But they are for defense-purpose shelters as well," a Kawasaki Heavy spokesperson said.

"It is assumed that there's going to be occasions in which people will have to take refuge in shelters for such a purpose."

Prime Minister Fumio Kishida has recently said that Japan was in the severest security environment since the end of World War II.

Referring to Russia's invasion of Ukraine, Kishida has also said what's happening to Ukraine could happen in east Asia "tomorrow."

The Kawasaki Heavy announcement comes a day after Russian President Vladimir Putin signed a deal with North Korean leader Kim Jong Un that included a mutual defense pledge.

Tokyo Gov. Yuriko Koike, who is campaigning for a third term, has pledged to set up shelters to protect 14 million residents in the capital from potential missile attacks.

Kawasaki Heavy, which, as a submarine manufacturer, already has expertise in air supply control in confined spaces, said the planned ventilators will be capable of removing poisonous gas as well as small particles in the air.

It has yet to be set how much the ventilators will sell for, the spokesperson said.