North Korea fired multiple ballistic missiles towards the sea off its eastern coast on Monday, South Korea’s military said. The launches marked Pyongyang’s fourth missile test in a month and followed Seoul’s recent hypersonic missile test.

South Korea’s Joint Chiefs of Staff said the missiles appeared to be of different types. They were launched from near Pyongyang at around 9:20 a.m. local time. One type travelled more than 900 km.

Japan’s coast guard earlier reported two unidentified projectiles, believed to be ballistic missiles, and said both appeared to have fallen. The US Pacific Command said it was aware of the launches but added that they posed no immediate threat to US personnel, territory or allies.

"We are aware of the missile launches and are consulting closely with our allies and partners," the statement said.

South Korea’s National Security Office held an emergency meeting following the launches. It condemned the tests as violations of United Nations Security Council resolutions and urged North Korea to stop them immediately.

North Korea has faced UN sanctions since 2006 over its nuclear weapons and ballistic missile programmes.

The latest launches come amid rising tensions between the two Koreas following a series of weapons tests. Last week, South Korean President Lee Jae Myung oversaw the country’s first test-firing of a hypersonic missile. The event was a rare public display of a missile test under a South Korean president.

A spokesperson for South Korea’s Joint Chiefs of Staff described Monday’s launches as "a show of force in response to the successful test launch of our hypersonic missile, as well as an intentional demonstration of missile capabilities".

North Korea last tested a ballistic missile on October 3. State media KCNA reported that leader Kim Jong Un supervised a hypersonic missile test.

Ballistic missiles follow a mostly unpowered flight path after launch. Hypersonic missiles travel at more than five times the speed of sound and are often designed to manoeuvre during flight.

The tests also follow a landmine explosion near the border last month that injured three South Korean soldiers. Seoul blamed North Korea for planting the mines and demanded an apology. Pyongyang rejected the accusation and accused South Korea of provocation.

North Korea has conducted missile tests on more than 10 occasions this year, including four in the past month.

Song Seong-jong, a professor at Daejeon University in Seoul and a former South Korean Defence Ministry official, said the frequent launches could strengthen Pyongyang’s position ahead of a potential summit between Kim and US President Donald Trump.

"They definitely need to raise the value of their status before meeting Trump," Song said.