Inter-Korean tensions mount after North Korea test-fires missiles

Inter-Korean tensions escalated as North Korea test-fired ballistic and cruise missiles off its eastern coast.

North Korea test-fired three ship-to-ship missiles off its north-east coast on Saturday, Xinhua reported, citing quotes issued by the South Korean military.

North Korea's official news agency also reported on Saturday that the nation had successfully test-fired a ballistic missile from a submarine. Their leader Kim Jong Un had issued an order to begin the test-firing and watched the test.

The test-firing came after North Korea issued warnings of "direct aimed strikes without any prior notice" against any South Korean navy patrol ship that infiltrated the disputed western sea border.

North Korea's south-western front command issued the warning on Friday, saying 17 South Korean naval boats had intruded into its territorial waters in the past seven days.

The warning was sent via a military communication line to South Korea's presidential office Cheong Wa Dae.

Another warning notice was sent to Seoul on Saturday.

The North Korea-claimed incursion was a repeat of a long-standing inter-Korean dispute over the maritime boundary.

Seoul sees the Northern Limit Line (NLL), which was drawn by US-led forces after the Korean War ended in 1953, as an official demarcation line, while Pyongyang demands that the border be further south.

The South Korean military said on Friday that it will "sternly" retaliate against any North Korean provocations.

North Korea's announcement of its success in firing a submarine-launched ballistic missile (SLBM) could prove to be a powerful nuclear threat to the US mainland as well as South Korea.

Pyongyang has previously test-fired long-range ballistic missiles, including inter-continental ballistic missiles (ICBM), five times and these developments have resulted in a widespread belief that Pyongyang is capable of striking the US mainland.

While the ICBMs can be detected before launches by surveillance satellites, the SLBM is very hard to detect. It could trigger an overhaul in South Korea's missile defence system.