North Korea says it has successfully test-fired a ballistic missile from a submarine and strengthened its nuclear attack capabilities.

Hours before the announcement by North Korea's state media Sunday, South Korean military officials said the North had fired what appeared to be a ballistic missile from a submarine off its eastern coast.

While South Korean experts say it's unlikely that North Korea currently possesses an operational submarine that can fire multiple missiles,

they acknowledge that the North is making progress on such technology.

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