Sales of nuclear shelters and radiation-blocking air purifiers have surged in Japan in recent weeks as North Korea has pressed ahead with missile tests in defiance of U.N. sanctions.

A small company that specializes in building nuclear shelters, generally under people's houses, has received eight orders in April alone, compared with six orders during a typical year.

The company, Oribe Seiki Seisakusho, based in Kobe, has also sold out of 50 Swiss-made air purifiers, which are designed to keep out radiation and poisonous gas, and is trying to get more, said Nobuko Oribe, the company's director.