The Democratic People's Republic of Korea says its latest ballistic missile tests were simulated pre-emptive strikes against South Korean ports and airfields used by the US military.

The DPRK says the tests were personally monitored by its leader Kim Jong-Un. On Tuesday morning, the DPRK fired three ballistic missiles into the sea off its east coast, possibly in a show of force against the deployment of an advanced anti-missile system in South Korea.

Meanwhile, strings of numbers have been broadcast over the radio from the DPRK. Officials in South Korea cannot confirm the intentions for the broadcast, but have urged the DPRK to cease such practices.