US detects 'unprecedented' submarine activity in North Korean waters

The US has raised concerns about "unprecedented levels" of North Korean submarine activity and underwater launch tests.

A US defence official told CNN that North Korea – which has a fleet of approximately 70 submarines – has been performing ejection tests, which is the first stage needed to launch a ballistic missile out of a sub.

The test reportedly occurred at the Sinpo Naval Shipyard on Sunday and is the third of its kind in less than a month.

The US official said the test coincides with unprecedented submarine activity and reports the rogue nation now has the capability to launch an intercontinental missile at the US.

"We will handle North Korea. We are gonna be able to handle them. It will be handled. We handle everything," US President Donald Trump told reporters during a Cabinet meeting.

However, he didn't stipulate how the US plans to deal with Pyongyang and Kim Jong-un's regime.

US intelligence believes North Korea has an arsenal of approximately 70 submarines, however many are thought to be obsolete and lacking the capability of firing missiles.

The submarine tests are thought to be North Korea's attempts at completing a "Strategic Triad," which involves having a land, sea and air-based nuclear arsenal to deter enemy attacks.

The US military has maintained heavy surveillance on North Korean submarine activity following the 2010 Cheonan incident where a North Korean sub torpedoed a South Korean ship.

As tensions to continue to mount between to two nations, the US successfully tested a missile interception system it hopes to set up on the Korean peninsula.

The US said it was the 15th successful intercept in 15 tests of the THAAD system, which stands for Terminal High Altitude Area Defence.