Footage of a North Korean submarine-launched ballistic missile (SLBM) test released by Pyongyang two days after it announced it had conducted the country's fourth nuclear test last week was faked, according to an analysis by a California-based think tank.

In defiance of a U.N. ban, the isolated country has said it has ballistic missile technology which will allow it to launch a nuclear warhead from a submarine, although experts and analysis of North Korean state media cast doubt on the claim.

North Korean state television aired footage Friday of the latest test, said to have taken place in December. Unlike a previous SLBM test in May, it had not been announced at the time.